Fix typo in doc

theories/base.v

@@ -65,7 +65,7 @@ Hint Extern 0 (TCNoBackTrack _) => constructor; apply _ : typeclass_instances.
 
 (* A conditional at the type class level. Note that [TCIf P Q R] is not the same
 as [TCOr (TCAnd P Q) R]: the latter will backtrack to [R] if it fails to
-establish [R], i.e. does not have the behavior of a conditional. Furthermore,
+establish [Q], i.e. does not have the behavior of a conditional. Furthermore,
 note that [TCOr (TCAnd P Q) (TCAnd (TCNot P) R)] would not work; we generally
 would not be able to prove the negation of [P]. *)
 Inductive TCIf (P Q R : Prop) : Prop :=