There seems to be a rather egregious problem with my commentary in the key to homework 4. At the very top of page 4, it says “Here, the two daughters are 2 and 4, and 2 is a function from…” and which point it goes off into bizarro world. 2 is in fact a function from properties to properties, which would be type <<e,t>,<e,t>>. (But even in the narrow context of the sentence it is wrong, a function from properties to truth values, which I said it was, is type <<e,t>,t>.)

Sorry for missing that in my proofreading.