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Aristotle’s Logic

Aristotle’s logic covers Aristotle’s understanding of how to reason as well as his understanding of what the various disciplines are and how they work. Aristotle’s logic is closely connected to his metaphysics, his understanding of human nature and his understanding of knowledge. The point of logic is to increase knowledge. So we can divide the field of logic into methods of acquiring knowledge, divisions of knowledge and objects of knowledge.

There are two methods for acquiring knowledge in Aristotle’s system. One of them is dialectic. That system starts with opinions that are common and accepted and explores the logical consequences of those opinions. It is primarily used to refute opinions that have problems. The other method for acquiring knowledge is scientific deduction. This deduction always results in greater knowledge. That is why it is called scientific. (Scientific does not have anything to do with modern science.) Scientific knowledge begins with sense experience and ends in knowledge and uses deductive methods and human reason to do so. Both methods also use definitions and rhetoric when it is necessary.

Aristotle divides knowledge into three categories. There are the theoretical sciences, ethical sciences and productive sciences. The theoretical sciences discover truth in the world. They include the natural sciences, philosophy and math. The ethical sciences tell us what to do. They include ethics and politics. The productive sciences make things. They include English, carpentry, rocket scientists and the like. Sciences always find what they are looking for. So theoretical sciences always find the truth (never error), ethical sciences always tell us the right thing to do and productive sciences always give us what they intend to. If these sciences do not, then that is because we were not following them correctly.

Aristotle divides the objects of knowledge into what is known as the ten categories. The ten categories explain that we either know truths about substances, or truths about various kinds of accidents. This is a preliminary look at his substance theory. He also explains how language points in various ways to these sorts of metaphysical truths. If substances are prior in knowledge to accidents, then definitions of accidents will always include substances. This has implications for what makes definitions good and also explains why logic is so tightly connected to metaphysics in his system.