Cognition covers the arts of problem solving. The Logic field of study covers any activity that studies Reason in order to manifest the material. Logic is the study of the principles of valid Inference and Demonstration. The word derives from Greek λογική (logike), fem. of λογικός (logikos), "possessed of reason, intellectual, dialectical, argumentative", from λόγος logos, "word, thought, idea, argument, account, reason, or principle".