Inductive reasoning
Induction, the collecting of facts, is not by itself science. The philosopher Hume said it meant “instances of which we have had no experience resemble those of which we have had experience”. Later, John Stuart Mill raised the question “Why is a single instance, in some cases, sufficient for a complete induction, while in others [many examples] go such a little way towards establishing a universal proposition?”  Philosophers usually think the real issue is: what distinguishes good from bad inductions? A way to say it is: "If all known As are B, then probably all As whatever are B".