If there is a Lark in the forest, it follows that every bird is fond of at least one bird. Why?
We start from the definition of the Lark:
L(x)(y) => x(y(y));Now, for y, swap in L(x):
L(x)(L(x)) => x(L(x)(L(x)));Voilà! x is fond of L(x)(L(x)). (Smullyan notes that this general fact will be useful for later problems.)