Backwards Arguing

After reading Michael Levin's essay, I found myself thinking about the fact that his method of argumentation seemed somewhat flipped when compared to many of the other philosophers in this book.  They mostly presented premises and evidence, and then considered only conclusions which did not contradict that evidence.  They may have guessed at their conclusions at the start, but in general their arguments began with premises and ended with conclusions.  Levin, on the other hand, appears to have started with an agenda and then refused to consider premises which might contradict it.  This is somewhat annoying, because it results in an argument which is only coherent on the surface; because Levin did not take into account any evidence which suggested a conclusion different from the one he supported.