(The `T` combinator in the derivations above is given by `T x <~~> \f. f x`;
it handles situations in which English word order reverses
-the usual function/argument order.)
+the usual function/argument order. `T` is what Curry and Steedman call this
+combinator. Jacobson calls it "lift", but it shouldn't be confused with the
+`mid` and `map` operations that lift values into the Reader monad we're focusing
+on here. It does lift values into a *different* monad, that we'll consider in
+a few weeks.)
In other words,
Jacobson's variable-free semantics is essentially a Reader monad.