You may have heard of Occam’s razor: the principle that given many competing explanations we should prefer those that make the fewest assumptions. Today we meet Hanlon, the lesser known of the razors. But why all the razors in the first place? The term “razor” in this case means a mental shortcut that helps us to “shave off” unlikely explanations. Razors are intended as a guide—a first line of defence—rather than anything final or definitive.