The idea, first presented (to my knowledge) in "Zen and the Art of Motorcycle Maintenance", that, for every hypothesis you can come up with to explain a given phenomenon, you will generate more questions about said phenomenon, and about your hypothesis itself, which will result in further hypothesizing, and in other potential explanations for the phenomenon in question. These hypothesis (hypothesii?) will, in turn, generate yet more hypothesis (hypothesises?). And so on, ad infinitum.