Why is logic a branch of philosophy?

Logic (from the Greek "logos", which has a variety of meanings including word, thought, idea, argument, account, reason or principle) is the study of reasoning, or the study of the principles and criteria of valid inference and demonstration. It attempts to distinguish good reasoning from bad reasoning. read more

Logic is a branch of philosophy because philosophy deals with wisdom which correlates with reasoning, you can't have wisdom without sound reasoning, logic is defined as the way and manner in which people differentiate bad and incorrect reasoning(Fallacy) from Good and correct reasoning. read more

Logic in Islamic philosophy also contributed to the development of modern logic, especially the development of Avicennian logic (which was responsible for the introduction of the hypothetical syllogism, temporal logic, modal logic and inductive logic) as an alternative to Aristotelian logic. read more

Psychologically, philosophy is an attitude, an approach, or a calling to answer, or to ask, or even to comment upon certain peculiar problems (i.e., problems such as those usually in the main branches of philosophy discussed below). read more