Aristotle was the founder of logic, and later investigation has not superseded his work but extended the feild. From the beginning , its has been known as the laws of thought . They are the law of identity, contradiction and excluded middle. A common technique of thinking called as Deductive is largely reducible to syllogism . The investigation of deduction and the elaboration of the syllogism are the work of Aristotle, and the Aristotelian Logic has been the logic of school and men in general.