− | '''Logic''' (from [[Ancient Greek|Classical Greek]] λόγος [[logos]]; meaning word, thought, idea, argument, account, reason, or principle) is the study of the principles and criteria of valid [[inference]] and [[demonstration (proof)|demonstration]]. | + | '''Logic''' (from [[Ancient Greek|Classical Greek]] λόγος [[logos]]; meaning word, thought, idea, argument, account, reason, or principle) is the study of valid [[inference]] and [[demonstration (proof)|demonstration]]. |