The Babbling Stream of Consciousness

you can. that's the point. he says "given a giraffe," not "given a giraffe and nothing else," so you can assume you are given what you would normally have available, the same way you can assume to have theorems that have already been proven for any particular problem without saying stuff like "given 1 + 1 = 2". the main difference is that b² doesn't know what you'd have in real life, so you can go ahead and say you have anything. don't try that in logical argument on a test though, because there he knows what tools you have available.