Logic is essential to Apologetics because “logic” is the foundation of all rational thought. Without logic we could not “know” anything about anything. We wouldn’t even be able to discuss the concept of logic.
Since logic is the foundation of all thought, it is then the basis of all thought regarding God (theology). Without logic, God would not be able to communicate truth to us. God is a rational being and he created us in His likeness.
Logic is necessary to understanding the Word of God and we are told in Hebrews 5:14 that strong meat belongs to the spiritually mature who through practice have vigorously exercised their use of the faculty of the mind for perceiving, understanding, and judging to distinguish good from bad.
Although Aristotle has been credited with “inventing” the Discipline of Logic, he didn’t actually invent logic itself, he simply discovered it and articulated it. The Discipline of Logic deals with the methods of valid thinking—drawing a proper conclusion from a premise. Basically, logic is putting your thoughts in order.
There are four fundamental laws of rational thought or logic that are crucial for use in Apologetics. They are part of a larger group which are called “first principles” without which nothing can be known. They are:
The law (or principle) of noncontradiction
The law (or principle) of identity
The law (or principle) of excluded middle
The law (or principle) of rational inference
The law of noncontradiction says that no two contradictory statements can be true at the same time and in the same sense. In other words, opposites cannot be the same and opposites cannot both be true.
The law of identity says that a thing must be identical to itself. If it isn’t then it would not be itself. Everything has an absolute identity. For example, a triangle is a shape that has three sides. That is its absolute identity. A rectangle is a shape that has four sides. A triangle cannot be a rectangle and a rectangle cannot be a triangle.
The law of excluded middle says that since opposites cannot be the same, nothing can hide in the “cracks” between being and nonbeing. The only choices are being or nonbeing. Either a triangle is a triangle or it is not, there is no inbetween. Either a person exists or he doesn’t exist.
The law of rational inference is used extensively in deductive logic through a specific type of argument called a Syllogism. A Syllogism consists of a Major premise, a Minor premise and a Conclusion. For example:
Major Premise: All men are mortal.
Minor Premise: John Smith is a man.
Conclusion: John Smith is mortal.
If the first two statements are true, then this guarantees the truth of the conclusion. This argument is then said to be “valid.” Arguments which are valid and have true premises are called “sound” arguments. However an argument can be “valid” but not a “sound” argument because one or both of the premises are false which will lead to a false conclusion.
“Valid” refers to the form of the Syllogism. “Sound” refers to the truth of the two premises used in a valid Syllogism.
