1. Cosmological Argument
Thomas Aquinas’s most famous proof of God refuses to go away. You’ve probably already heard of it in some form. It was around before Aquinas, at least as early as Plato and Aristotle, and in basic terms, it goes like this:
1. Every finite and contingent being has a cause.
2. Nothing finite and contingent can cause itself.
3. A causal chain cannot be of infinite length.
4. Therefore, a First Cause (or something that is not an effect) must exist.
This is especially impressive in that it was theorized by the Ancient Greeks, at a time when the Universe was not known to have had an origin. Today, we call this “the Big Bang,” and the argument has changed to this form:
1. Whatever begins to exist has a cause.
2. The Universe began to exist.
3. Therefore, the Universe had a cause.
Sequentially speaking, these three points are true. But the second point requires the Universe to have had a cause, and we still aren’t sure it did. “The Big Bang” is the most prevalent astrophysical theory today, but it has its detractors, most arguing that because the mathematics that leads back to a big bang do not function at the point immediately prior to the big bang, those mathematics were invalid to begin with.
Better than this, however, is the argument that this proof of God commits the logical fallacy called “infinite regression.” If the Universe had a first cause, what caused that first cause? Criticism declares that it is unfair to argue for every thing’s cause, and then argue for the sole exception of a “First Cause,” which did not have a cause.
2. Argument from Reason
One of my favorites, with very intricate abstraction. C. S. Lewis (who wrote “The Lion, the Witch, and the Wardrobe”) came up with this. It begins as an argument from design, and then continues into something new. Very basically, it argues that God must exist, because, in Lewis’s words:
“Supposing there was no intelligence behind the universe, no creative mind. In that case, nobody designed my brain for the purpose of thinking. It is merely that when the atoms inside my skull happen, for physical or chemical reasons, to arrange themselves in a certain way, this gives me, as a by-product, the sensation I call thought. But, if so, how can I trust my own thinking to be true? It’s like upsetting a milk jug and hoping that the way it splashes itself will give you a map of London. But if I can’t trust my own thinking, of course I can’t trust the arguments leading to Atheism, and therefore have no reason to be an Atheist, or anything else. Unless I believe in God, I cannot believe in thought: so I can never use thought to disbelieve in God.”
It sounds powerful, and the final judgment on it is still out there. But its primary weak point is that, in the strictest sense, it is not a proof of God’s existence because it requires the assumption that human minds can assess the truth or falsehood of a claim, and it requires that human minds can be convinced by argumentation.
But in order to reject the assumption that human minds can assess the truth or falsehood of a claim, a human mind must assume that this claim is true or false, which immediately proves that human minds can assess the truth or falsehood of a claim.
But none of this has anything to do with God’s existence. Thus, the argument is better treated as a disproof of naturalistic materialism. However, given that most Atheists use naturalistic materialism as the foundation of Atheism, is is a very viable argument.
3. Argument from Degree
This is one of St. Thomas Aquinas’s “Five Proofs of God,” and still causes debate among the two sides. Here is Aquinas’s statement of it, which I have translated from Latin, for a sense of thoroughness:
The fourth proof originates from the degrees discovered in things. For there is discovered greater and lesser degrees of goodness, truth, nobility, and others. But “more” or “less” are terms spoken concerning various things that approach in diverse manners toward something that is the “greatest,” just as in the case of “hotter” approaching nearer the “greatest” heat. There exists, therefore, something “truest,” and “best,” and “noblest,” which, in consequence, is the “greatest” being. For those things which are the greatest truths are the greatest beings, as is stated in Metaphysics Bk. II. 2. Furthermore, that which is the greatest in its way, is, in another way, the cause of all things belonging to it; thus fire, which is the greatest heat, is the cause of all heat, as is said in the same book (cf. Plato and Aristotle). Therefore, there exists something that is the cause of the existence of all things, and of goodness, and of every perfection whatever. We call this “God.”
The most prevalent criticism of this argument considers that we do not have to believe in an object of a greater degree in order to believe in an object of a lesser degree. Richard Dawkins, the most famous, or infamous, Atheist around these days, argues that just because we come across a “smelly” object, does not require that we believe that we believe in a “preeminently peerless stinker,” in his words.
4. Moral Argument
This argument is very old, and states that God must exist for the following reason: 1. An aspect of morality is observed. 2. Belief in God is a better explanation for this morality than any alternative. 3. Belief in God is thus preferable to disbelief in God.
This argument is technically valid, provided that the three constituents are accepted, and most critics refuse to accept the first. Morality, they argue, is not universal. Murder was perfectly fine for the soldiers of the First Crusade, who slaughtered every man, woman, and child in Jerusalem in 1099. Thomas Hobbes argued that morality is based on the society around it, and is thus not objective.
This argument is quite brazen in its simplicity, requiring not only a belief in God, but a belief in the necessity of God. If you believe he is necessary, then you must believe he exists.
Criticism typically deals with the Ontological Argument committing a “bare assertion fallacy,” which means it asserts qualities inherent solely to an unproven statement, without any support for those qualities. It is also criticized as a circular argument, revolving from a premise to a conclusion which relies on the premise, which relies on the conclusion.