09:06
As before, we need the lemma that the union of any finite set of finite collections is finite. The trick is to first construct a function f on the nodes such that if x has an infinite subtree then f(x) is a child node with an infinite subtree. This is possible because of the lemma. Now we can then build the path using f and the recursion theorem.
This is possible because for any path that ends at a node x with an infinite subtree, f(x) is a child node with an infinite subtree and so we can extend the path to f(x). Since f is a function, we are not making any choice here.
So the only use of CCF is to construct f.
Oh wait there's something wrong.
←
4 messages moved from Logic