Section ZL'.
Variable T:Type.
Variable R:relation T.
Hypothesis ord:order R.
Definition chain (S: Ensemble T) : Prop :=
forall x y:T, In S x -> In S y -> (R x y \/ R y x).
Definition maximal (x:T) : Prop :=
forall y:T, R x y -> x = y.
Variable chain_sup: forall S: Ensemble T, chain S ->
{ x:T | (forall y:T, In S y -> R y x) /\
(forall z:T, (forall y:T, In S y -> R y z) -> R x z) }.
Variable inflation: forall x:T,
{ y:T | R x y /\ x <> y /\ forall z:T, R x z -> R z y ->
z = x \/ z = y }.
Inductive tower : Ensemble T :=
| sup_intro: forall (S: Ensemble T), Included S tower ->
forall c:chain S,
In tower (proj1_sig (chain_sup S c))
| inflation_intro: forall x:T, In tower x ->
In tower (proj1_sig (inflation x)).

Lemma tower_is_chain: chain tower.