diff --git a/doc/lean/tutorial.org b/doc/lean/tutorial.org index d5559e3b6..a020c1586 100644 --- a/doc/lean/tutorial.org +++ b/doc/lean/tutorial.org @@ -639,12 +639,12 @@ equality are all dependent functions. The universal quantifier is just a dependent function. In Lean, if we have a family of types =B : A → Prop=, -then =∀ x : A, B a= has type =Prop=. +then =∀ a : A, B a= has type =Prop=. This feature complicates the Lean set-theoretic model, but it improves usability. Several theorem provers have a =forall elimination= (aka instantiation) proof rule. -In Lean (and other systems based on proposition as types), this rule +In Lean (and other systems based on propositions as types), this rule is just function application. In the following example we add an axiom stating that =f x= is =0= forall =x=.