Modus Tollens Modus tollens is another deductive rule of inference frequently used in mathematics including beginning algebra. The general expression for modus tollens is the following: P → Q (First premise is a conditional statement) ¬ Q (Second premise is the negation of the consequent) ¬ P (Conclusion deduced is the negation of the

# Category: Background Information

# Introduction to Deductive Reasoning and Mathematics III

Before examining some formal rules of deductive logic, we should observe that Aristotle invented logic and we should examine the three so-called Fundamental Rules of Thought which he formulated. You may read more about Aristotle’s involvement with the beginnings of logic. https://oregonstate.edu/instruct/phl201/modules/Philosophers/Aristotle/aristotle_laws_of_thought.html The Three Fundamental Rules of Thought The Law of Identity Whatever is, is;