Popper distinguished between the creative and informal process from which theories and accepted basic statements emerge and the logical and formal process where theories are falsified or corroborated. The main issue is whether the decision to select a theory among competing theories in the light of falsifications and corroborations should be moved in the logical part as some kind of formal logic. It is a delicate question, because this logic would be inductive: it selects a universal law in view of instances. The answer of Lakatos and many others to that question is that it should. In contradistinction, for Popper, the creative and informal part is guided by methodological rules, which naturally say to favor theories that are corroborated, but this methodology can hardly be made rigorous. Popper does not discuss corroborations when he describes the purely logical part.