We all take for granted that knowledge is possible. One needn’t be arrogant in order to confidently hold that there are at least some things—actually, a great number of things—that we can claim to know. I know that I exist, that I know that I know that I exist, that I have a body, that I’m sitting here in front of my laptop typing these words, that I have a son, and that 2+2=4.
Knowledge is inseparable from reason, logic, and meaning.
We wouldn’t be able to have a single coherent, meaningful thought unless we implicitly knew the truth of the most fundamental laws of logic: The Law of Identity, The Law of Non-Contradiction, and The Law of Excluded Middle.
The Law of Identity is simply the principle that a thing is what it is, and is not what it is not. (“A car is a car. It is not a bike.”)
The Law of Non-Contradiction is the principle that a thing can’t be and not be in the same respect and at the same time. (“A person can never be simultaneously pregnant and not pregnant.”)
The Law of Excluded Middle is the principle that either something is or it is not. (“Either the person is pregnant or is not pregnant.”)
These are the principles in the absence of which thinking itself—all of our reasonings, as well as the intelligibility of our experiences, great and small—would be impossible. We don’t arrive at the principles of logic through rational argument. They are the basis for the possibility of any arguments. We don’t discover the principles through experience. Experience presupposes the principles, for experience is never an indecipherable, chaotic mess of sense impressions, but, rather, an ordered, intelligible event.
The principles of logic, then, are the preconditions for the very possibility of knowledge in all of its forms. But an inquiry into the origins of the knowledge that we take for granted can’t end there. We need to ask ourselves: What kind of a thing is a principle of logic?
In other words, what is the ontological status of a principle?
Now, if the atheist is correct and the cosmos is, ultimately, nothing more or less than matter-in-motion, then, it would seem, the principles of logic would have to be reducible to the physical. This, however, is impossible.
Matter exists in time and in space. But the principles of logic are bound by neither time nor space. They are true always and forever. To put the point another way, the principles of logic are universal and timeless: They would remain true even if the cosmos self-destructed at this moment, or even if it never began to exist at all.
The principles, that is, do not begin, and they have no expiration date.
Matter is perpetually mutating. The principles of logic, though, are immutable.
The principles of logic, the preconditions of knowledge, reason, experience—comprehensively, of thought—are mental. They are the stuff of mind. Yet they can’t originate in my mind or your mind, for our minds are finite and incessantly changing. The principles, though, to repeat, are infinite and changeless.
Thus, they must be grounded in a mind that is infinite and changeless as well.
And this is the Mind of God.
No one denies the principles of logic, for in order to deny them, you must affirm them. Take, for instance, the Law of Non-Contradiction. Aristotle noted long ago that to take a position against the truth of this law is to endorse the truth of it, for in attempting to negate the principle, the arguer recognizes that a position and its negation can’t be simultaneously true. Either the Law of Non-Contradiction is true or it is not. It can’t be both.
Some critics of TAG have responded by asserting that the laws of logic just are; we needn’t appeal to God. This, though, is an inadequate response in that it fails to account for how infinite, timeless, changeless concepts can exist in a world that is alleged to be purely material and always in flux.
In contrast, the proponents of TAG account for the principles of logic by viewing them as pointing beyond themselves to God. With God, however, it is indeed enough to say that God just is. God, by definition, is identical with His Being. He is unique insofar as He does not depend, and cannot depend, upon anything for His existence. That the logic of the concept of the Supreme Being entails that the Supreme Being must, well, be, doesn’t prove that God really exists, of course. But it’s valuable in highlighting that the question, “Why does God exist?” is nonsensical in a way that an inquiry into the ground of the principles of logic is not. To ask, “Why God?” is like asking, “Why does a square have four sides?” The answer to the latter is: “It’s a square. The essence of a square is to be four-sided.” Similarly, it is the essence of the Supreme Being to be.
This, at any rate, is the crux of the Transcendental Argument for God (TAG).