DEFINITION pr3_iso_appl_bind()
TYPE =
       ∀b:B
         .not (eq B b Abst)
           →∀v1:T
                .∀v2:T
                  .∀t:T
                    .let u1 := THead (Flat Appl) v1 (THead (Bind b) v2 t)
                    in ∀c:C
                           .∀u2:T
                             .pr3 c u1 u2
                               →((iso u1 u2)→∀P:Prop.P
                                    →pr3 c (THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)) u2)
BODY =
        assume b: B
        suppose H: not (eq B b Abst)
        assume v1: T
        assume v2: T
        assume t: T
          we must prove 
                let u1 := THead (Flat Appl) v1 (THead (Bind b) v2 t)
                in ∀c:C
                       .∀u2:T
                         .pr3 c u1 u2
                           →((iso u1 u2)→∀P:Prop.P
                                →pr3 c (THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)) u2)
          or equivalently 
                ∀c:C
                  .∀u2:T
                    .pr3 c (THead (Flat Appl) v1 (THead (Bind b) v2 t)) u2
                      →((iso (THead (Flat Appl) v1 (THead (Bind b) v2 t)) u2)→∀P:Prop.P
                           →pr3 c (THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)) u2)
           assume c: C
           assume u2: T
           suppose H0: pr3 c (THead (Flat Appl) v1 (THead (Bind b) v2 t)) u2
           suppose H1: (iso (THead (Flat Appl) v1 (THead (Bind b) v2 t)) u2)→∀P:Prop.P
             (H2) 
                by (pr3_gen_appl . . . . H0)

                   or3
                     ex3_2
                       T
                       T
                       λu2:T.λt2:T.eq T u2 (THead (Flat Appl) u2 t2)
                       λu2:T.λ:T.pr3 c v1 u2
                       λ:T.λt2:T.pr3 c (THead (Bind b) v2 t) t2
                     ex4_4
                       T
                       T
                       T
                       T
                       λ:T.λ:T.λu2:T.λt2:T.pr3 c (THead (Bind Abbr) u2 t2) u2
                       λ:T.λ:T.λu2:T.λ:T.pr3 c v1 u2
                       λy1:T.λz1:T.λ:T.λ:T.pr3 c (THead (Bind b) v2 t) (THead (Bind Abst) y1 z1)
                       λ:T.λz1:T.λ:T.λt2:T.∀b:B.∀u:T.(pr3 (CHead c (Bind b) u) z1 t2)
                     ex6_6
                       B
                       T
                       T
                       T
                       T
                       T
                       λb:B.λ:T.λ:T.λ:T.λ:T.λ:T.not (eq B b Abst)
                       λb:B.λy1:T.λz1:T.λ:T.λ:T.λ:T.pr3 c (THead (Bind b) v2 t) (THead (Bind b) y1 z1)
                       λb:B
                         .λ:T
                           .λ:T
                             .λz2:T.λu2:T.λy2:T.pr3 c (THead (Bind b) y2 (THead (Flat Appl) (lift (S O) O u2) z2)) u2
                       λ:B.λ:T.λ:T.λ:T.λu2:T.λ:T.pr3 c v1 u2
                       λ:B.λy1:T.λ:T.λ:T.λ:T.λy2:T.pr3 c y1 y2
                       λb:B.λ:T.λz1:T.λz2:T.λ:T.λy2:T.pr3 (CHead c (Bind b) y2) z1 z2
             end of H2
             we proceed by induction on H2 to prove pr3 c (THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)) u2
                case or3_intro0 : H3:ex3_2 T T λu3:T.λt2:T.eq T u2 (THead (Flat Appl) u3 t2) λu3:T.λ:T.pr3 c v1 u3 λ:T.λt2:T.pr3 c (THead (Bind b) v2 t) t2 ⇒
                   the thesis becomes pr3 c (THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)) u2
                      we proceed by induction on H3 to prove pr3 c (THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)) u2
                         case ex3_2_intro : x0:T x1:T H4:eq T u2 (THead (Flat Appl) x0 x1) :pr3 c v1 x0 :pr3 c (THead (Bind b) v2 t) x1 ⇒
                            the thesis becomes pr3 c (THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)) u2
                               (H7) 
                                  we proceed by induction on H4 to prove 
                                     (iso
                                         THead (Flat Appl) v1 (THead (Bind b) v2 t)
                                         THead (Flat Appl) x0 x1)
                                       →∀P:Prop.P
                                     case refl_equal : ⇒
                                        the thesis becomes the hypothesis H1

                                     (iso
                                         THead (Flat Appl) v1 (THead (Bind b) v2 t)
                                         THead (Flat Appl) x0 x1)
                                       →∀P:Prop.P
                               end of H7
                               by (iso_head . . . . .)
                               we proved 
                                  iso
                                    THead (Flat Appl) v1 (THead (Bind b) v2 t)
                                    THead (Flat Appl) x0 x1
                               by (H7 previous .)
                               we proved 
                                  pr3
                                    c
                                    THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                    THead (Flat Appl) x0 x1
                               by (eq_ind_r . . . previous . H4)
pr3 c (THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)) u2
pr3 c (THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)) u2
                case or3_intro1 : H3:ex4_4 T T T T λ:T.λ:T.λu3:T.λt2:T.pr3 c (THead (Bind Abbr) u3 t2) u2 λ:T.λ:T.λu3:T.λ:T.pr3 c v1 u3 λy1:T.λz1:T.λ:T.λ:T.pr3 c (THead (Bind b) v2 t) (THead (Bind Abst) y1 z1) λ:T.λz1:T.λ:T.λt2:T.∀b0:B.∀u:T.(pr3 (CHead c (Bind b0) u) z1 t2) ⇒
                   the thesis becomes pr3 c (THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)) u2
                      we proceed by induction on H3 to prove pr3 c (THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)) u2
                         case ex4_4_intro : x0:T x1:T x2:T x3:T H4:pr3 c (THead (Bind Abbr) x2 x3) u2 H5:pr3 c v1 x2 H6:pr3 c (THead (Bind b) v2 t) (THead (Bind Abst) x0 x1) H7:∀b0:B.∀u:T.(pr3 (CHead c (Bind b0) u) x1 x3) ⇒
                            the thesis becomes pr3 c (THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)) u2
                               (H_x) 
                                  by (pr3_gen_bind . H . . . . H6)

                                     or
                                       ex3_2
                                         T
                                         T
                                         λu2:T.λt2:T.eq T (THead (Bind Abst) x0 x1) (THead (Bind b) u2 t2)
                                         λu2:T.λ:T.pr3 c v2 u2
                                         λ:T.λt2:T.pr3 (CHead c (Bind b) v2) t t2
                                       pr3 (CHead c (Bind b) v2) t (lift (S O) O (THead (Bind Abst) x0 x1))
                               end of H_x
                               (H8) consider H_x
                               we proceed by induction on H8 to prove 
                                  pr3
                                    c
                                    THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                    THead (Bind Abbr) x2 x3
                                  case or_introl : H9:ex3_2 T T λu3:T.λt2:T.eq T (THead (Bind Abst) x0 x1) (THead (Bind b) u3 t2) λu3:T.λ:T.pr3 c v2 u3 λ:T.λt2:T.pr3 (CHead c (Bind b) v2) t t2 ⇒
                                     the thesis becomes 
                                     pr3
                                       c
                                       THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                       THead (Bind Abbr) x2 x3
                                        we proceed by induction on H9 to prove 
                                           pr3
                                             c
                                             THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                             THead (Bind Abbr) x2 x3
                                           case ex3_2_intro : x4:T x5:T H10:eq T (THead (Bind Abst) x0 x1) (THead (Bind b) x4 x5) H11:pr3 c v2 x4 H12:pr3 (CHead c (Bind b) v2) t x5 ⇒
                                              the thesis becomes 
                                              pr3
                                                c
                                                THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                                THead (Bind Abbr) x2 x3
                                                 (H13) 
                                                    by (f_equal . . . . . H10)
                                                    we proved 
                                                       eq
                                                         B
                                                         <λ:T.B>
                                                           CASE THead (Bind Abst) x0 x1 OF
                                                             TSort ⇒Abst
                                                           | TLRef ⇒Abst
                                                           | THead k  ⇒<λ:K.B> CASE k OF Bind b0⇒b0 | Flat ⇒Abst
                                                         <λ:T.B>
                                                           CASE THead (Bind b) x4 x5 OF
                                                             TSort ⇒Abst
                                                           | TLRef ⇒Abst
                                                           | THead k  ⇒<λ:K.B> CASE k OF Bind b0⇒b0 | Flat ⇒Abst

                                                       eq
                                                         B
                                                         λe:T
                                                             .<λ:T.B>
                                                               CASE e OF
                                                                 TSort ⇒Abst
                                                               | TLRef ⇒Abst
                                                               | THead k  ⇒<λ:K.B> CASE k OF Bind b0⇒b0 | Flat ⇒Abst
                                                           THead (Bind Abst) x0 x1
                                                         λe:T
                                                             .<λ:T.B>
                                                               CASE e OF
                                                                 TSort ⇒Abst
                                                               | TLRef ⇒Abst
                                                               | THead k  ⇒<λ:K.B> CASE k OF Bind b0⇒b0 | Flat ⇒Abst
                                                           THead (Bind b) x4 x5
                                                 end of H13
                                                 (h1) 
                                                    (H14) 
                                                       by (f_equal . . . . . H10)
                                                       we proved 
                                                          eq
                                                            T
                                                            <λ:T.T> CASE THead (Bind Abst) x0 x1 OF TSort ⇒x0 | TLRef ⇒x0 | THead  t0 ⇒t0
                                                            <λ:T.T> CASE THead (Bind b) x4 x5 OF TSort ⇒x0 | TLRef ⇒x0 | THead  t0 ⇒t0

                                                          eq
                                                            T
                                                            λe:T.<λ:T.T> CASE e OF TSort ⇒x0 | TLRef ⇒x0 | THead  t0 ⇒t0
                                                              THead (Bind Abst) x0 x1
                                                            λe:T.<λ:T.T> CASE e OF TSort ⇒x0 | TLRef ⇒x0 | THead  t0 ⇒t0 (THead (Bind b) x4 x5)
                                                    end of H14
                                                    (h1) 
                                                       (H15) 
                                                          by (f_equal . . . . . H10)
                                                          we proved 
                                                             eq
                                                               T
                                                               <λ:T.T> CASE THead (Bind Abst) x0 x1 OF TSort ⇒x1 | TLRef ⇒x1 | THead   t0⇒t0
                                                               <λ:T.T> CASE THead (Bind b) x4 x5 OF TSort ⇒x1 | TLRef ⇒x1 | THead   t0⇒t0

                                                             eq
                                                               T
                                                               λe:T.<λ:T.T> CASE e OF TSort ⇒x1 | TLRef ⇒x1 | THead   t0⇒t0
                                                                 THead (Bind Abst) x0 x1
                                                               λe:T.<λ:T.T> CASE e OF TSort ⇒x1 | TLRef ⇒x1 | THead   t0⇒t0 (THead (Bind b) x4 x5)
                                                       end of H15
                                                        suppose H16: eq T x0 x4
                                                        suppose H17: eq B Abst b
                                                          (H18) 
                                                             consider H15
                                                             we proved 
                                                                eq
                                                                  T
                                                                  <λ:T.T> CASE THead (Bind Abst) x0 x1 OF TSort ⇒x1 | TLRef ⇒x1 | THead   t0⇒t0
                                                                  <λ:T.T> CASE THead (Bind b) x4 x5 OF TSort ⇒x1 | TLRef ⇒x1 | THead   t0⇒t0
                                                             that is equivalent to eq T x1 x5
                                                             by (eq_ind_r . . . H12 . previous)
pr3 (CHead c (Bind b) v2) t x1
                                                          end of H18
                                                          (H21) 
                                                             by (eq_ind_r . . . H . H17)
not (eq B Abst Abst)
                                                          end of H21
                                                          we proceed by induction on H17 to prove 
                                                             pr3
                                                               c
                                                               THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                                               THead (Bind Abbr) x2 x3
                                                             case refl_equal : ⇒
                                                                the thesis becomes 
                                                                pr3
                                                                  c
                                                                  THead (Bind Abst) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                                                  THead (Bind Abbr) x2 x3
                                                                   (H22) 
                                                                      by (refl_equal . .)
                                                                      we proved eq B Abst Abst
                                                                      by (H21 previous)
                                                                      we proved False
                                                                      by cases on the previous result we prove 
                                                                         pr3
                                                                           c
                                                                           THead (Bind Abst) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                                                           THead (Bind Abbr) x2 x3

                                                                         pr3
                                                                           c
                                                                           THead (Bind Abst) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                                                           THead (Bind Abbr) x2 x3
                                                                   end of H22
                                                                   consider H22

                                                                      pr3
                                                                        c
                                                                        THead (Bind Abst) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                                                        THead (Bind Abbr) x2 x3
                                                          we proved 
                                                             pr3
                                                               c
                                                               THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                                               THead (Bind Abbr) x2 x3

                                                          eq T x0 x4
                                                            →(eq B Abst b
                                                                 →(pr3
                                                                      c
                                                                      THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                                                      THead (Bind Abbr) x2 x3))
                                                    end of h1
                                                    (h2) 
                                                       consider H14
                                                       we proved 
                                                          eq
                                                            T
                                                            <λ:T.T> CASE THead (Bind Abst) x0 x1 OF TSort ⇒x0 | TLRef ⇒x0 | THead  t0 ⇒t0
                                                            <λ:T.T> CASE THead (Bind b) x4 x5 OF TSort ⇒x0 | TLRef ⇒x0 | THead  t0 ⇒t0
eq T x0 x4
                                                    end of h2
                                                    by (h1 h2)

                                                       eq B Abst b
                                                         →(pr3
                                                              c
                                                              THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                                              THead (Bind Abbr) x2 x3)
                                                 end of h1
                                                 (h2) 
                                                    consider H13
                                                    we proved 
                                                       eq
                                                         B
                                                         <λ:T.B>
                                                           CASE THead (Bind Abst) x0 x1 OF
                                                             TSort ⇒Abst
                                                           | TLRef ⇒Abst
                                                           | THead k  ⇒<λ:K.B> CASE k OF Bind b0⇒b0 | Flat ⇒Abst
                                                         <λ:T.B>
                                                           CASE THead (Bind b) x4 x5 OF
                                                             TSort ⇒Abst
                                                           | TLRef ⇒Abst
                                                           | THead k  ⇒<λ:K.B> CASE k OF Bind b0⇒b0 | Flat ⇒Abst
eq B Abst b
                                                 end of h2
                                                 by (h1 h2)

                                                    pr3
                                                      c
                                                      THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                                      THead (Bind Abbr) x2 x3

                                           pr3
                                             c
                                             THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                             THead (Bind Abbr) x2 x3
                                  case or_intror : H9:pr3 (CHead c (Bind b) v2) t (lift (S O) O (THead (Bind Abst) x0 x1)) ⇒
                                     the thesis becomes 
                                     pr3
                                       c
                                       THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                       THead (Bind Abbr) x2 x3
                                        (h1) 
                                           by (drop_refl .)
                                           we proved drop O O c c
                                           that is equivalent to drop (r (Bind b) O) O c c
                                           by (drop_drop . . . . previous .)
                                           we proved drop (S O) O (CHead c (Bind b) v2) c
                                           by (pr3_lift . . . . previous . . H5)
                                           we proved pr3 (CHead c (Bind b) v2) (lift (S O) O v1) (lift (S O) O x2)
                                           by (pr3_flat . . . previous . . H9 .)
                                           we proved 
                                              pr3
                                                CHead c (Bind b) v2
                                                THead (Flat Appl) (lift (S O) O v1) t
                                                THead
                                                  Flat Appl
                                                  lift (S O) O x2
                                                  lift (S O) O (THead (Bind Abst) x0 x1)
                                           by (pr3_head_2 . . . . . previous)

                                              pr3
                                                c
                                                THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                                THead
                                                  Bind b
                                                  v2
                                                  THead
                                                    Flat Appl
                                                    lift (S O) O x2
                                                    lift (S O) O (THead (Bind Abst) x0 x1)
                                        end of h1
                                        (h2) 
                                           by (lift_flat . . . . .)
                                           we proved 
                                              eq
                                                T
                                                lift (S O) O (THead (Flat Appl) x2 (THead (Bind Abst) x0 x1))
                                                THead
                                                  Flat Appl
                                                  lift (S O) O x2
                                                  lift (S O) O (THead (Bind Abst) x0 x1)
                                           we proceed by induction on the previous result to prove 
                                              pr3
                                                c
                                                THead
                                                  Bind b
                                                  v2
                                                  THead
                                                    Flat Appl
                                                    lift (S O) O x2
                                                    lift (S O) O (THead (Bind Abst) x0 x1)
                                                THead (Bind Abbr) x2 x3
                                              case refl_equal : ⇒
                                                 the thesis becomes 
                                                 pr3
                                                   c
                                                   THead
                                                     Bind b
                                                     v2
                                                     lift (S O) O (THead (Flat Appl) x2 (THead (Bind Abst) x0 x1))
                                                   THead (Bind Abbr) x2 x3
                                                    (h1) 
                                                       (h1) by (pr0_refl .) we proved pr0 x2 x2
                                                       (h2) by (pr0_refl .) we proved pr0 x1 x1
                                                       by (pr0_beta . . . h1 . . h2)
                                                       we proved 
                                                          pr0
                                                            THead (Flat Appl) x2 (THead (Bind Abst) x0 x1)
                                                            THead (Bind Abbr) x2 x1
                                                       by (pr0_zeta . H . . previous .)
                                                       we proved 
                                                          pr0
                                                            THead
                                                              Bind b
                                                              v2
                                                              lift (S O) O (THead (Flat Appl) x2 (THead (Bind Abst) x0 x1))
                                                            THead (Bind Abbr) x2 x1
                                                       by (pr2_free . . . previous)

                                                          pr2
                                                            c
                                                            THead
                                                              Bind b
                                                              v2
                                                              lift (S O) O (THead (Flat Appl) x2 (THead (Bind Abst) x0 x1))
                                                            THead (Bind Abbr) x2 x1
                                                    end of h1
                                                    (h2) 
                                                       (h1) by (pr3_refl . .) we proved pr3 c x2 x2
                                                       (h2) 
                                                          by (H7 . .)
pr3 (CHead c (Bind Abbr) x2) x1 x3
                                                       end of h2
                                                       by (pr3_head_12 . . . h1 . . . h2)
pr3 c (THead (Bind Abbr) x2 x1) (THead (Bind Abbr) x2 x3)
                                                    end of h2
                                                    by (pr3_sing . . . h1 . h2)

                                                       pr3
                                                         c
                                                         THead
                                                           Bind b
                                                           v2
                                                           lift (S O) O (THead (Flat Appl) x2 (THead (Bind Abst) x0 x1))
                                                         THead (Bind Abbr) x2 x3

                                              pr3
                                                c
                                                THead
                                                  Bind b
                                                  v2
                                                  THead
                                                    Flat Appl
                                                    lift (S O) O x2
                                                    lift (S O) O (THead (Bind Abst) x0 x1)
                                                THead (Bind Abbr) x2 x3
                                        end of h2
                                        by (pr3_t . . . h1 . h2)

                                           pr3
                                             c
                                             THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                             THead (Bind Abbr) x2 x3
                               we proved 
                                  pr3
                                    c
                                    THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                    THead (Bind Abbr) x2 x3
                               by (pr3_t . . . previous . H4)
pr3 c (THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)) u2
pr3 c (THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)) u2
                case or3_intro2 : H3:ex6_6 B T T T T T λb0:B.λ:T.λ:T.λ:T.λ:T.λ:T.not (eq B b0 Abst) λb0:B.λy1:T.λz1:T.λ:T.λ:T.λ:T.pr3 c (THead (Bind b) v2 t) (THead (Bind b0) y1 z1) λb0:B.λ:T.λ:T.λz2:T.λu3:T.λy2:T.pr3 c (THead (Bind b0) y2 (THead (Flat Appl) (lift (S O) O u3) z2)) u2 λ:B.λ:T.λ:T.λ:T.λu3:T.λ:T.pr3 c v1 u3 λ:B.λy1:T.λ:T.λ:T.λ:T.λy2:T.pr3 c y1 y2 λb0:B.λ:T.λz1:T.λz2:T.λ:T.λy2:T.pr3 (CHead c (Bind b0) y2) z1 z2 ⇒
                   the thesis becomes pr3 c (THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)) u2
                      we proceed by induction on H3 to prove pr3 c (THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)) u2
                         case ex6_6_intro : x0:B x1:T x2:T x3:T x4:T x5:T H4:not (eq B x0 Abst) H5:pr3 c (THead (Bind b) v2 t) (THead (Bind x0) x1 x2) H6:pr3 c (THead (Bind x0) x5 (THead (Flat Appl) (lift (S O) O x4) x3)) u2 H7:pr3 c v1 x4 H8:pr3 c x1 x5 H9:pr3 (CHead c (Bind x0) x5) x2 x3 ⇒
                            the thesis becomes pr3 c (THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)) u2
                               (H_x) 
                                  by (pr3_gen_bind . H . . . . H5)

                                     or
                                       ex3_2
                                         T
                                         T
                                         λu2:T.λt2:T.eq T (THead (Bind x0) x1 x2) (THead (Bind b) u2 t2)
                                         λu2:T.λ:T.pr3 c v2 u2
                                         λ:T.λt2:T.pr3 (CHead c (Bind b) v2) t t2
                                       pr3 (CHead c (Bind b) v2) t (lift (S O) O (THead (Bind x0) x1 x2))
                               end of H_x
                               (H10) consider H_x
                               we proceed by induction on H10 to prove 
                                  pr3
                                    c
                                    THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                    THead (Bind x0) x5 (THead (Flat Appl) (lift (S O) O x4) x3)
                                  case or_introl : H11:ex3_2 T T λu3:T.λt2:T.eq T (THead (Bind x0) x1 x2) (THead (Bind b) u3 t2) λu3:T.λ:T.pr3 c v2 u3 λ:T.λt2:T.pr3 (CHead c (Bind b) v2) t t2 ⇒
                                     the thesis becomes 
                                     pr3
                                       c
                                       THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                       THead (Bind x0) x5 (THead (Flat Appl) (lift (S O) O x4) x3)
                                        we proceed by induction on H11 to prove 
                                           pr3
                                             c
                                             THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                             THead (Bind x0) x5 (THead (Flat Appl) (lift (S O) O x4) x3)
                                           case ex3_2_intro : x6:T x7:T H12:eq T (THead (Bind x0) x1 x2) (THead (Bind b) x6 x7) H13:pr3 c v2 x6 H14:pr3 (CHead c (Bind b) v2) t x7 ⇒
                                              the thesis becomes 
                                              pr3
                                                c
                                                THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                                THead (Bind x0) x5 (THead (Flat Appl) (lift (S O) O x4) x3)
                                                 (H15) 
                                                    by (f_equal . . . . . H12)
                                                    we proved 
                                                       eq
                                                         B
                                                         <λ:T.B>
                                                           CASE THead (Bind x0) x1 x2 OF
                                                             TSort ⇒x0
                                                           | TLRef ⇒x0
                                                           | THead k  ⇒<λ:K.B> CASE k OF Bind b0⇒b0 | Flat ⇒x0
                                                         <λ:T.B>
                                                           CASE THead (Bind b) x6 x7 OF
                                                             TSort ⇒x0
                                                           | TLRef ⇒x0
                                                           | THead k  ⇒<λ:K.B> CASE k OF Bind b0⇒b0 | Flat ⇒x0

                                                       eq
                                                         B
                                                         λe:T
                                                             .<λ:T.B>
                                                               CASE e OF
                                                                 TSort ⇒x0
                                                               | TLRef ⇒x0
                                                               | THead k  ⇒<λ:K.B> CASE k OF Bind b0⇒b0 | Flat ⇒x0
                                                           THead (Bind x0) x1 x2
                                                         λe:T
                                                             .<λ:T.B>
                                                               CASE e OF
                                                                 TSort ⇒x0
                                                               | TLRef ⇒x0
                                                               | THead k  ⇒<λ:K.B> CASE k OF Bind b0⇒b0 | Flat ⇒x0
                                                           THead (Bind b) x6 x7
                                                 end of H15
                                                 (h1) 
                                                    (H16) 
                                                       by (f_equal . . . . . H12)
                                                       we proved 
                                                          eq
                                                            T
                                                            <λ:T.T> CASE THead (Bind x0) x1 x2 OF TSort ⇒x1 | TLRef ⇒x1 | THead  t0 ⇒t0
                                                            <λ:T.T> CASE THead (Bind b) x6 x7 OF TSort ⇒x1 | TLRef ⇒x1 | THead  t0 ⇒t0

                                                          eq
                                                            T
                                                            λe:T.<λ:T.T> CASE e OF TSort ⇒x1 | TLRef ⇒x1 | THead  t0 ⇒t0 (THead (Bind x0) x1 x2)
                                                            λe:T.<λ:T.T> CASE e OF TSort ⇒x1 | TLRef ⇒x1 | THead  t0 ⇒t0 (THead (Bind b) x6 x7)
                                                    end of H16
                                                    (h1) 
                                                       (H17) 
                                                          by (f_equal . . . . . H12)
                                                          we proved 
                                                             eq
                                                               T
                                                               <λ:T.T> CASE THead (Bind x0) x1 x2 OF TSort ⇒x2 | TLRef ⇒x2 | THead   t0⇒t0
                                                               <λ:T.T> CASE THead (Bind b) x6 x7 OF TSort ⇒x2 | TLRef ⇒x2 | THead   t0⇒t0

                                                             eq
                                                               T
                                                               λe:T.<λ:T.T> CASE e OF TSort ⇒x2 | TLRef ⇒x2 | THead   t0⇒t0 (THead (Bind x0) x1 x2)
                                                               λe:T.<λ:T.T> CASE e OF TSort ⇒x2 | TLRef ⇒x2 | THead   t0⇒t0 (THead (Bind b) x6 x7)
                                                       end of H17
                                                        suppose H18: eq T x1 x6
                                                        suppose H19: eq B x0 b
                                                          (H20) 
                                                             consider H17
                                                             we proved 
                                                                eq
                                                                  T
                                                                  <λ:T.T> CASE THead (Bind x0) x1 x2 OF TSort ⇒x2 | TLRef ⇒x2 | THead   t0⇒t0
                                                                  <λ:T.T> CASE THead (Bind b) x6 x7 OF TSort ⇒x2 | TLRef ⇒x2 | THead   t0⇒t0
                                                             that is equivalent to eq T x2 x7
                                                             by (eq_ind_r . . . H14 . previous)
pr3 (CHead c (Bind b) v2) t x2
                                                          end of H20
                                                          (H21) 
                                                             by (eq_ind_r . . . H13 . H18)
pr3 c v2 x1
                                                          end of H21
                                                          (H22) 
                                                             we proceed by induction on H19 to prove pr3 (CHead c (Bind b) x5) x2 x3
                                                                case refl_equal : ⇒
                                                                   the thesis becomes the hypothesis H9
pr3 (CHead c (Bind b) x5) x2 x3
                                                          end of H22
                                                          (h1) by (pr3_t . . . H21 . H8) we proved pr3 c v2 x5
                                                          (h2) 
                                                             (h1) 
                                                                by (drop_refl .)
                                                                we proved drop O O c c
                                                                that is equivalent to drop (r (Bind b) O) O c c
                                                                by (drop_drop . . . . previous .)
                                                                we proved drop (S O) O (CHead c (Bind b) v2) c
                                                                by (pr3_lift . . . . previous . . H7)
pr3 (CHead c (Bind b) v2) (lift (S O) O v1) (lift (S O) O x4)
                                                             end of h1
                                                             (h2) 
                                                                by (pr3_pr3_pr3_t . . . H8 . . . H22)
                                                                we proved pr3 (CHead c (Bind b) x1) x2 x3
                                                                by (pr3_pr3_pr3_t . . . H21 . . . previous)
                                                                we proved pr3 (CHead c (Bind b) v2) x2 x3
                                                                by (pr3_t . . . H20 . previous)
pr3 (CHead c (Bind b) v2) t x3
                                                             end of h2
                                                             by (pr3_flat . . . h1 . . h2 .)

                                                                pr3
                                                                  CHead c (Bind b) v2
                                                                  THead (Flat Appl) (lift (S O) O v1) t
                                                                  THead (Flat Appl) (lift (S O) O x4) x3
                                                          end of h2
                                                          by (pr3_head_21 . . . h1 . . . h2)
                                                          we proved 
                                                             pr3
                                                               c
                                                               THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                                               THead (Bind b) x5 (THead (Flat Appl) (lift (S O) O x4) x3)
                                                          by (eq_ind_r . . . previous . H19)
                                                          we proved 
                                                             pr3
                                                               c
                                                               THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                                               THead (Bind x0) x5 (THead (Flat Appl) (lift (S O) O x4) x3)

                                                          eq T x1 x6
                                                            →(eq B x0 b
                                                                 →(pr3
                                                                      c
                                                                      THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                                                      THead (Bind x0) x5 (THead (Flat Appl) (lift (S O) O x4) x3)))
                                                    end of h1
                                                    (h2) 
                                                       consider H16
                                                       we proved 
                                                          eq
                                                            T
                                                            <λ:T.T> CASE THead (Bind x0) x1 x2 OF TSort ⇒x1 | TLRef ⇒x1 | THead  t0 ⇒t0
                                                            <λ:T.T> CASE THead (Bind b) x6 x7 OF TSort ⇒x1 | TLRef ⇒x1 | THead  t0 ⇒t0
eq T x1 x6
                                                    end of h2
                                                    by (h1 h2)

                                                       eq B x0 b
                                                         →(pr3
                                                              c
                                                              THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                                              THead (Bind x0) x5 (THead (Flat Appl) (lift (S O) O x4) x3))
                                                 end of h1
                                                 (h2) 
                                                    consider H15
                                                    we proved 
                                                       eq
                                                         B
                                                         <λ:T.B>
                                                           CASE THead (Bind x0) x1 x2 OF
                                                             TSort ⇒x0
                                                           | TLRef ⇒x0
                                                           | THead k  ⇒<λ:K.B> CASE k OF Bind b0⇒b0 | Flat ⇒x0
                                                         <λ:T.B>
                                                           CASE THead (Bind b) x6 x7 OF
                                                             TSort ⇒x0
                                                           | TLRef ⇒x0
                                                           | THead k  ⇒<λ:K.B> CASE k OF Bind b0⇒b0 | Flat ⇒x0
eq B x0 b
                                                 end of h2
                                                 by (h1 h2)

                                                    pr3
                                                      c
                                                      THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                                      THead (Bind x0) x5 (THead (Flat Appl) (lift (S O) O x4) x3)

                                           pr3
                                             c
                                             THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                             THead (Bind x0) x5 (THead (Flat Appl) (lift (S O) O x4) x3)
                                  case or_intror : H11:pr3 (CHead c (Bind b) v2) t (lift (S O) O (THead (Bind x0) x1 x2)) ⇒
                                     the thesis becomes 
                                     pr3
                                       c
                                       THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                       THead (Bind x0) x5 (THead (Flat Appl) (lift (S O) O x4) x3)
                                        (h1) 
                                           by (drop_refl .)
                                           we proved drop O O c c
                                           that is equivalent to drop (r (Bind b) O) O c c
                                           by (drop_drop . . . . previous .)
                                           we proved drop (S O) O (CHead c (Bind b) v2) c
                                           by (pr3_lift . . . . previous . . H7)
                                           we proved pr3 (CHead c (Bind b) v2) (lift (S O) O v1) (lift (S O) O x4)
                                           by (pr3_flat . . . previous . . H11 .)
                                           we proved 
                                              pr3
                                                CHead c (Bind b) v2
                                                THead (Flat Appl) (lift (S O) O v1) t
                                                THead
                                                  Flat Appl
                                                  lift (S O) O x4
                                                  lift (S O) O (THead (Bind x0) x1 x2)
                                           by (pr3_head_2 . . . . . previous)

                                              pr3
                                                c
                                                THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                                THead
                                                  Bind b
                                                  v2
                                                  THead
                                                    Flat Appl
                                                    lift (S O) O x4
                                                    lift (S O) O (THead (Bind x0) x1 x2)
                                        end of h1
                                        (h2) 
                                           by (lift_flat . . . . .)
                                           we proved 
                                              eq
                                                T
                                                lift (S O) O (THead (Flat Appl) x4 (THead (Bind x0) x1 x2))
                                                THead
                                                  Flat Appl
                                                  lift (S O) O x4
                                                  lift (S O) O (THead (Bind x0) x1 x2)
                                           we proceed by induction on the previous result to prove 
                                              pr3
                                                c
                                                THead
                                                  Bind b
                                                  v2
                                                  THead
                                                    Flat Appl
                                                    lift (S O) O x4
                                                    lift (S O) O (THead (Bind x0) x1 x2)
                                                THead (Bind x0) x5 (THead (Flat Appl) (lift (S O) O x4) x3)
                                              case refl_equal : ⇒
                                                 the thesis becomes 
                                                 pr3
                                                   c
                                                   THead
                                                     Bind b
                                                     v2
                                                     lift (S O) O (THead (Flat Appl) x4 (THead (Bind x0) x1 x2))
                                                   THead (Bind x0) x5 (THead (Flat Appl) (lift (S O) O x4) x3)
                                                    (h1) 
                                                       (h1) by (pr0_refl .) we proved pr0 x4 x4
                                                       (h2) by (pr0_refl .) we proved pr0 x1 x1
                                                       (h3) by (pr0_refl .) we proved pr0 x2 x2
                                                       by (pr0_upsilon . H4 . . h1 . . h2 . . h3)
                                                       we proved 
                                                          pr0
                                                            THead (Flat Appl) x4 (THead (Bind x0) x1 x2)
                                                            THead (Bind x0) x1 (THead (Flat Appl) (lift (S O) O x4) x2)
                                                       by (pr0_zeta . H . . previous .)
                                                       we proved 
                                                          pr0
                                                            THead
                                                              Bind b
                                                              v2
                                                              lift (S O) O (THead (Flat Appl) x4 (THead (Bind x0) x1 x2))
                                                            THead (Bind x0) x1 (THead (Flat Appl) (lift (S O) O x4) x2)
                                                       by (pr2_free . . . previous)

                                                          pr2
                                                            c
                                                            THead
                                                              Bind b
                                                              v2
                                                              lift (S O) O (THead (Flat Appl) x4 (THead (Bind x0) x1 x2))
                                                            THead (Bind x0) x1 (THead (Flat Appl) (lift (S O) O x4) x2)
                                                    end of h1
                                                    (h2) 
                                                       by (pr3_thin_dx . . . H9 . .)
                                                       we proved 
                                                          pr3
                                                            CHead c (Bind x0) x5
                                                            THead (Flat Appl) (lift (S O) O x4) x2
                                                            THead (Flat Appl) (lift (S O) O x4) x3
                                                       by (pr3_head_12 . . . H8 . . . previous)

                                                          pr3
                                                            c
                                                            THead (Bind x0) x1 (THead (Flat Appl) (lift (S O) O x4) x2)
                                                            THead (Bind x0) x5 (THead (Flat Appl) (lift (S O) O x4) x3)
                                                    end of h2
                                                    by (pr3_sing . . . h1 . h2)

                                                       pr3
                                                         c
                                                         THead
                                                           Bind b
                                                           v2
                                                           lift (S O) O (THead (Flat Appl) x4 (THead (Bind x0) x1 x2))
                                                         THead (Bind x0) x5 (THead (Flat Appl) (lift (S O) O x4) x3)

                                              pr3
                                                c
                                                THead
                                                  Bind b
                                                  v2
                                                  THead
                                                    Flat Appl
                                                    lift (S O) O x4
                                                    lift (S O) O (THead (Bind x0) x1 x2)
                                                THead (Bind x0) x5 (THead (Flat Appl) (lift (S O) O x4) x3)
                                        end of h2
                                        by (pr3_t . . . h1 . h2)

                                           pr3
                                             c
                                             THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                             THead (Bind x0) x5 (THead (Flat Appl) (lift (S O) O x4) x3)
                               we proved 
                                  pr3
                                    c
                                    THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)
                                    THead (Bind x0) x5 (THead (Flat Appl) (lift (S O) O x4) x3)
                               by (pr3_t . . . previous . H6)
pr3 c (THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)) u2
pr3 c (THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)) u2
             we proved pr3 c (THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)) u2
          we proved 
             ∀c:C
               .∀u2:T
                 .pr3 c (THead (Flat Appl) v1 (THead (Bind b) v2 t)) u2
                   →((iso (THead (Flat Appl) v1 (THead (Bind b) v2 t)) u2)→∀P:Prop.P
                        →pr3 c (THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)) u2)
          that is equivalent to 
             let u1 := THead (Flat Appl) v1 (THead (Bind b) v2 t)
             in ∀c:C
                    .∀u2:T
                      .pr3 c u1 u2
                        →((iso u1 u2)→∀P:Prop.P
                             →pr3 c (THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)) u2)
       we proved 
          ∀b:B
            .not (eq B b Abst)
              →∀v1:T
                   .∀v2:T
                     .∀t:T
                       .let u1 := THead (Flat Appl) v1 (THead (Bind b) v2 t)
                       in ∀c:C
                              .∀u2:T
                                .pr3 c u1 u2
                                  →((iso u1 u2)→∀P:Prop.P
                                       →pr3 c (THead (Bind b) v2 (THead (Flat Appl) (lift (S O) O v1) t)) u2)