Does Logic Presuppose Christianity? — Part 2: What Is Logic?

In the introductory post of this series, I mentioned that I would be attempting to provide clarity to the ideas behind the Van Tillian argument from logic. One thing that definitely needs clarification before we examine the nuances behind the actual argument is what exactly is meant by the term “logic”. 

The term “logic” is susceptible to a host of varying definitions and interpretations. Often times, both parties have different things in mind when thinking about logic in the context of the argument. This often leads to both sides talking past each other. What exactly does the Van Tillian means when he uses the term logic?

Laws of Logic 

In most cases, the covenantal apologist had the three classical laws of logic in mind when he uses the term logic in his argument. Logic, then, is simply meant to be a shorthand term for laws of logic. The three classical laws of logic include: (1) the law of identity, (2) the law of non-contradiction, and (3) the law of excluded middle. These are usually what the Van Tillian has in mind when he uses the term. As Bahnsen says in his debate with Dr. Stein:

When we go to look at the different world views that atheists and theists have, I suggest we can prove the existence of God from the impossibility of the contrary. The transcendental proof for God's existence is that without Him it is impossible to prove anything. The atheist world view is irrational and cannot consistently provide the preconditions of intelligible experience, science, logic, or morality. The atheist world view cannot allow for laws of logic, the uniformity of nature, the ability for the mind to understand the world, and moral absolutes.

From this, it is clear that Bahnsen referred to laws of logic when he used the term “logic”. However, the term “laws of logic” actually carries some ambiguity as well. Although most times it is used to refer to the three classical laws of logic, it may sometimes refer to something different. Laws of logic may refer to the following:

1. Rules of inference: laws of logic can be used to refer to inferential rules such as modus ponens or modus tollens. 

2. Standards of rationality (Epistemic Norms): laws of logic are often referred to as laws of thought. That is, they can be seen as standards for correct or acceptable reasoning. In this case, they are seen as normative; prescribing how we ought to reason.

3. Logical truths: “logic” or “laws of logic” could also refer to broadly logical truths.

The terms “logic” or “laws of logic” could refer to all these. It is important, then, for both parties to be clear on what exactly is meant when the term is used. It may be argued that whatever sense the term is used, the argument proceeds the same way. This may be true but for the sake of clarity, it must be made clear what sense one is using the terms as discussions such as these could become complex really fast. In the next post, we shall begin to examine the different arguments for the claim that logic presupposes Christianity.