Caveat: both logic and reason are extraordinarily rich fields in philosophy, and my talk of them here does little justice to them. There are, for example, many logics beyond the classical logic that I touch on. I provide links to more rigorous treatments at the end. See also this piece which previously tackled the Logic Fetishist phenomenon. Lastly, logic (informal or otherwise) is a valuable tool for thought, and the misuse of the term “logic” doesn’t bear on its proper use.

Suppose that someone accuses you of being illogical, alleging that you should — as they do — use reason to come to your senses. You should invoke facts. You should stop being emotional and instead appeal to logic. What do they mean by logic? Are they accusing you of having constructed deductively invalid arguments? Perhaps they mean you’ve improperly quantified over some domain? Whatever they mean, logic and reason are supposed to carry weight. Your accuser takes their own beliefs to have some special status, to be imbued with a special force. It’s thought to be bad to be illogical or unresponsive to reason. Yet your accuser belongs to a group that has appropriated logic and reason from the contexts that grant them this special power. They’ve stolen the terms, severing them from their source. Call this group the Logic Fetishists. I hope to show that the heist carried out by the Logic Fetishists leaves their usage of “logic” and “reason” impotent. I’ll also go over where exactly the force the terms exert over discourse is sourced. But first, what do logicians and philosophers mean by logic and reason?

A Very Brief Introduction to Logic

Skip this if you‘re familiar with elementary sentential logic/FOL.

In asserting that a proposition, or sentence, is true, we can be expected to provide an argument in favor of it. An argument is any set of sentences, one of which is the conclusion and the rest of which are premises. Formal logic deals strictly with the form of arguments, with the relation between premises and conclusions. The logician has in their toolkit various methods to determine whether an argument is deductively valid, or whether it is impossible for all the premises to be true and the conclusion false. If we transcribe English sentences into a formal language, we’re usually equipped to evaluate an argument’s validity. Consider the following arguments (*) and (^):

(*)

If my friend is in jail, then it will rain. My friend is in jail. Therefore, it will rain.

(^)

If your house is on fire, then you should probably leave. Your house is on fire. Therefore, you should probably leave.

Both are valid and of the same form. If we assume that their premises are true, their conclusion must follow. Formal logic is blind to what all of these sentences mean in natural language: it only sees their structure. Roughly, a partial transcription of these sentences into our formal language will look like:

If P, then Q P Therefore, Q

Formal logic isn’t all there is. Some valid arguments are bad, and many invalid arguments are good. While valid, (*) is not a very good argument. While often invalid, many scientific arguments are good. An inductive (i.e., the premises confer support on, but do not logically entail, the conclusion) example:

The sun rose in the east yesterday. The sun rose in the east the day before yesterday. The sun rose in the east the day before the day before yesterday. The sun has risen in the east for (insert massive amount of days here). Our scientists expect no special anomaly in the sun’s rise tomorrow. Therefore, the sun will rise in the east tomorrow.

If the premises evaluate as true, we aren’t forced to accept the conclusion on pain of logical inconsistency; we merely have good reason to. While an introduction to formal logic will leave out the details regarding the logic of induction, there’s a large background literature.

Is all of this what the Logic Fetishist means by “logic?” I don’t think so.

What is Rationality?

What rationality means is far less than transparent than logic. It’s also the subject of much contention in philosophy. Just as there are many kinds of logic, so too are there many kinds of rationality. Let’s look at what some philosophers have said about rationality:

Behavior is procedurally rational when it is the outcome of appropriate deliberation. Its procedural rationality depends on the process that generated it. When psychologists use the term “rational,” it is usually procedural rationality they have in mind.¹ According to theories of instrumental rationality, we have a reason to do something just in case (A) doing this thing might help to fulfill one of our present desires. According to theories of deliberative rationality, we have such a reason just in case (B) if we knew the relevant facts, and went through some process of deliberation, we would be motivated to do this thing.² By epistemic rationality, I mean, roughly, the kind of rationality which one displays when one believes propositions that are strongly supported by one’s evidence and refrains from believing propositions that are improbable given one’s evidence.³

So, there are various uses of reason and rationality at play. What’s important is whether the Logic Fetishist has any of these uses — or anything in the neighborhood — in mind. Would it be epistemically rational to believe that the Logic Fetishist cares deeply about the substantive philosophical work needed to get an account of rationality off the ground? Do they know what they’re talking about when they construe your position as irrational, construing their own beliefs as satisfying whatever requirements rationality imposes on us? Probably not.

The Normative Force of Logic and Reason

I’ve so far given little reason to believe that the Logic Fetishist is confused about logic and reason. But their confusion would not matter if neither logic nor reason had any special force. You will remain unmoved was I to tell you that I dislike your arguments. Calling your beliefs “ugly” leaves you unconvinced of whatever it is that I’m selling. So, logic and reason pack a punch that my personal dislike doesn’t. The force they carry is normative — they constrain what we ought believe and the procedures we ought engage in to generate beliefs. They regulate our thoughts and behavior. As we might expect, there is debate in philosophy not only over the content of logic’s normative force, but over whether it has any normative force at all. Nevertheless, the Logic Fetishist’s theft of logic and reason relies on the existence of this normative force, so I will take it for granted. I’ll also take for granted that logic and reason make requirements of us similar to the following:

You should not believe both P and not-P.

If you believe that “If P, then Q” and “P,” you should believe “Q.” More generally, you should believe (within reason) what is logically entailed by the beliefs you already hold.

You should A if you believe that you ought A.

You can only believe P if P is epistemically accessible to you (e.g., you’re in a position to know that P).

That logic and reason could ever make such requirements of us is, of course, sourced in their meanings and in the background literature in philosophy. Formal logic gives us standards (albeit highly constrained ones) for good reasoning. It offers us tools to check whether or not the arguments we make and confront satisfy those standards. Moreover, those who deliberate about the requirements rationality might make of us are philosophers. Were we to ignore the work that philosophers have done, what would remain of rationality? If we moved to a context in which logic meant “what makes sense to Zach,” we would feel no force to satisfy the requirements that this new logic makes of us. This is where the Logic Fetishist’s appeal to logic and reason becomes impotent. They make use of the terms — stealing their normative force from philosophy — but leave behind the source that grants the terms their normative force.

When the Logic Fetishist tells us that our argument is illogical, they do not mean that it is deductively invalid or inductively poor. When they tell you to use facts, you are rightly confused because you believed yourself to be debating what the facts themselves are. In their accusations of irrationality you will find that no substantive work has been done to establish that we’ve run afoul of, for example, the requirement to believe P only if P is epistemically accessible to us. They are not interested in the philosophical discourse surrounding rationality and what it requires of us. This would be okay but for the theft. Others also use “logic” and technical terms from logic in ways that fail to correspond exactly to what we mean by the terms in philosophy (e.g., “that’s a valid point”). Unless we’re snobs, we don’t make anything of it. The problem with the Logic Fetishist is that they want to change the usage of the terms but preserve their force (which is sourced in their original usage)!

Case Studies

Here are what I take to be paradigmatic cases of Logic Fetishists:

No matter how robust the output and foundations of climate science are, it’s not helpful to paint it as “simple logic:”

It weakens the case against the following:

I believe that these mostly speak for themselves and nicely illustrate how the Logic Fetishists navigate around the rich literature in which the normative force of logic and reason is sourced.

Here are some cases where Logic Fetishists come slightly closer to what we mean by logic and reason in philosophy, but still fall short along some dimension. I comment on each very, very briefly.

D’Souza often appeals to logic in ways that satisfy the Logic Fetishists’ usage. Here, he does appear to mean what logicians mean by logic, but it’s not very difficult to construct counterexamples that debunk his tweet:

Obama is ten feet tall. Humans don’t exist. Therefore, Trump is president.

The argument is invalid and the premises are false, but the conclusion is true. While he takes himself to be logically superior (whatever that might mean), he fares rather poorly with respect to logic.