Paul Stone wrote: "Yes, but that's not the case the way this problem is posed." I agree, but I understood you to be saying that there was a trivial answer that could be derived from the simple fact that he COULD (your emphasis) know what colour his hat is. If the answer requires the fact that neither P1 nor P2 know what colour their hats are, your answer is not trivial but rather just not expressing all the logical steps. Of course, it might be possible to intuit the answer without those steps but I thought Walter was interested in having those steps articulated. Sincerely, Phil Enns Toronto, ON ------------------------------------------------------------------ To change your Lit-Ideas settings (subscribe/unsub, vacation on/off, digest on/off), visit www.andreas.com/faq-lit-ideas.html