diff --git a/fol-subst.agda b/fol-subst.agda
new file mode 100644
index 0000000..cbd5ee1
--- /dev/null
+++ b/fol-subst.agda
@@ -0,0 +1,138 @@
+open import Data.Nat
+open import Relation.Binary.PropositionalEquality
+
+variable m n l : ℕ
+
+data Term : ℕ → Set where
+  zero : Term (suc n)
+  suc : Term n → Term (suc n)
+
+variable t u : Term n
+
+data Subst : ℕ → ℕ → Set where
+  ε : Subst n 0
+  _,_ : Subst m n → Term m → Subst m (suc n)
+
+suc-subst : Subst m n → Subst (suc m) n
+suc-subst ε = ε
+suc-subst (ts , t) = suc-subst ts , suc t
+
+id : Subst m m
+id {zero} = ε
+id {suc m} = (suc-subst (id {m})) , zero
+
+subst-t : Term m → Subst n m → Term n
+subst-t zero (us , u) = u
+subst-t (suc t) (us , u) = subst-t t us
+
+wk-t1 : Term n → Term (suc n)
+wk-t1 t = subst-t t (suc-subst id)
+
+subst-t1 : Term (suc n) → Term n → Term n
+subst-t1 t u = subst-t t (id , u)
+
+comp : Subst m l → Subst n m → Subst n l
+comp ε us = ε
+comp (ts , u) us = (comp ts us) , (subst-t u us)
+
+{-
+t [ suc vs ] ≡ suc (t [vs ])
+suc-subst ts ∘ (us , t) ≡ ts ∘ us
+
+t [ id ] ≡ t
+t [ us ∘ vs ] ≡ t [ us ] [ vs ]
+
+ts ∘ id ≡ ts
+id ∘ ts ≡ ts
+(ts ∘ us) ∘ vs ≡ ts ∘ (us ∘ vs)
+
+-}
+
+
+{-
+wk-t : (l : ℕ) → Term (l + n) → Term (suc (l + n))
+wk-t zero t = suc t
+wk-t (suc l) zero = zero
+wk-t (suc l) (suc t) = suc (wk-t l t)
+
+subst-t : (l : ℕ) → Term (suc (l + n)) → Term n → Term (l + n)
+subst-t zero zero u = u
+subst-t zero (suc t) u = t
+subst-t (suc l) zero u = zero
+subst-t (suc l) (suc t) u = suc (subst-t l t u)
+
+infix 15 _⇒_
+
+data Form : ℕ → Set where
+  _⇒_ : Form n → Form n → Form n
+  ∀F : Form (suc n) → Form n
+  P : Term n → Form n
+--  R : Term n → Term n → Form n
+
+wk-F : (l : ℕ) → Form (l + n) → Form (suc (l + n))
+wk-F l (A ⇒ B) = wk-F l A ⇒ wk-F l B
+wk-F l (∀F A) = ∀F (wk-F (suc l) A)
+wk-F l (P t) = P (wk-t l t)
+
+subst-F : (l : ℕ) → Form (suc (l + n)) → Term n → Form (l + n)
+subst-F l (A ⇒ B) u = subst-F l A u ⇒ subst-F l B u
+subst-F l (∀F A) u = ∀F (subst-F (suc l) A u)
+subst-F l (P t) u = P (subst-t l t u)
+
+infix 10 _▷_
+
+data Con : ℕ → Set where
+  • : Con n
+  _▷_ : Con n → Form n → Con n
+
+wk-C : (l : ℕ) → Con (l + n) → Con (suc (l + n))
+wk-C l • = •
+wk-C l (Γ ▷ A) = wk-C l Γ ▷ wk-F l A
+
+variable Γ Δ : Con n
+variable A B C : Form n
+
+infix 5 _⊢_ 
+
+data _⊢_ : Con n → Form n → Set where
+  zero : Γ ▷ A ⊢ A
+  suc : Γ ⊢ A → Γ ▷ B ⊢ A
+  lam : Γ ▷ A ⊢ B → Γ ⊢ A ⇒ B
+  app : Γ ⊢ A ⇒ B → Γ ⊢ A → Γ ⊢ B
+  Lam : (wk-C zero Γ) ⊢ A → Γ ⊢ ∀F A
+  App : Γ ⊢ ∀F A → (t : Term _) → Γ ⊢ subst-F zero A t
+
+{-
+-- (A ⇒ ∀ x . P x) ⇒ ∀ x . A → P x
+
+-- A ≡ A [ wk ][ < t > ] 
+
+wk-subst : subst l (wk l A) t ≡ t
+
+wk-subst :  (A [ wk ]F) s[ < t > ]F ≡ A
+wk-subst = {!!}
+
+example : • ⊢ (A ⇒ (∀F (P zero))) ⇒ (∀F (A [ wk ]F) ⇒ P zero)
+example {A = A} = lam (lam (App (app (suc zero) 
+         (subst (λ X → (• ▷ A ⇒ ∀F (P zero)) ▷ ∀F (A [ wk ]F) ⊢ X)
+           (wk-subst {A = A}) (App zero zero))) zero))
+
+
+-- (∀ x ∀ y . A(x,y)) ⇒ ∀ y ∀ x . A(y,x)
+-- (A ⇒ ∀ x . B(x)) ⇒ ∀ x . A ⇒ B(x)   
+-- ∀ x y . A(x,y) ⇒ ∀ x . A(x,x)
+-- ∀ x . A (x) ⇒ ∀ x y . A(x)
+-- (((∀ x . A (x)) ⇒ B)⇒ B) ⇒ ∀ x . ((A (x) ⇒ B) ⇒ B)
+
+-}
+
+--eqq : (suc (suc (l + n))) ≡ suc l + suc n
+eqq : (suc (l + n)) ≡ l + suc n
+eqq = {!!}
+
+eq : ∀ {t : Term (suc (l + n))}{u : Term n} →
+--   subst-t {n = suc n} l (subst Term (eqq {l = l}{n = n})(wk-t {n = n} (suc l) t)) (wk-t zero u)
+   subst-t {n = suc n} l (subst Term (eqq {l = (suc l)}{n = n})(wk-t {n = n} (suc l) t)) (wk-t zero u)
+   ≡ {! subst-t l t   !} -- subst-t l (wk-t (suc l) t) u ≡ subst-t l t u
+eq = {!!}
+-}
diff --git a/fol.agda b/fol.agda
index 678232a..2c8b577 100644
--- a/fol.agda
+++ b/fol.agda
@@ -84,3 +84,13 @@ example {A = A} = lam (lam (App (app (suc zero)
 -- (((∀ x . A (x)) ⇒ B)⇒ B) ⇒ ∀ x . ((A (x) ⇒ B) ⇒ B)
 
 -}
+
+--eqq : (suc (suc (l + n))) ≡ suc l + suc n
+eqq : (suc (l + n)) ≡ l + suc n
+eqq = {!!}
+
+eq : ∀ {t : Term (suc (l + n))}{u : Term n} →
+--   subst-t {n = suc n} l (subst Term (eqq {l = l}{n = n})(wk-t {n = n} (suc l) t)) (wk-t zero u)
+   subst-t {n = suc n} l (subst Term (eqq {l = (suc l)}{n = n})(wk-t {n = n} (suc l) t)) (wk-t zero u)
+   ≡ {! subst-t l t   !} -- subst-t l (wk-t (suc l) t) u ≡ subst-t l t u
+eq = {!!}