u/Dry_Journalist_7001

I’ve had a lot of back and forth on here recently asking about the reasoning process of a determinist. I’ve gotten answers ranging from “the reasoning process is in the causally determined process” to “I changed my mind and I realized it after the fact”. Huh?

How do those who deny the existence of free will reconcile the active process of logical inference with a universe where every mental state is a necessary byproduct of prior physical causes?

When I talk about reasoning, I’m not just talking about a sequence of thoughts. I’m talking about the evaluation of propositions based on logical laws. The "person" is actively filtering noise and choosing to follow the "thread of logic" over emotional bias or random impulse.

Let’s just grant the determinist defense: let's assume a purely physical, predetermined brain process can be called "reasoning," and that evolution built our brains to be "reliable truth-trackers."

The framework still collapses because of a fundamental mismatch between how physics works and how logic works. A thermometer is 100% determined by physics, and accurately tracks temperature. This works because temperature is a physical property directly acting on another physical property. Physics tracking physics makes perfect sense.

Logic is not a physical property. A logical fallacy doesn't have mass. A valid syllogism doesn't have an electrical charge. Soundness doesn't have velocity. Physical laws only react to physical forces. A neuron fires strictly because of chemical gradients and electrical thresholds. It cannot "see" or "react" to the abstract laws of logic. It doesn't know the difference between a sound argument and a confirmation bias, it just blindly executes the laws of physics.

This is where determinism hits a dead end:

If every mental state is entirely caused by prior physical events, then your brain transitions from thought A to thought B because of physical necessity, not logical necessity. Your neurochemistry is reacting to the physical state of your brain, not to the logical validity of your argument. In this framework, you aren't actually "weighing" evidence against an independent standard of logic. You cannot verify whether your current wiring is tracking objective truth or just executing a glitch.

If your "reasoning" is entirely pre-determined, then it is technically happening to you, not being performed by you. If determinism is true, your belief in it is just a biological inevitability.

This is the part where the computer analogy fails the determinist. A computer’s circuits can run logical software only because an outside programmer designed the hardware to mirror logic. But in a deterministic universe, there is no programmer. You are left asserting that non-rational physical forces, purely by accident, wired your brain to perfectly instantiate abstract laws of logic that possess no physical mass or force.

How do you bridge the gap between a conclusion that is merely physically caused and one that is epistemically justified? If your neurochemistry can only ever react to physical inputs, on what logical ground can you claim that a blind physical process is structurally capable of tracking abstract, non-physical logical truths?

A free will denier could have chosen to believe in free will. A libertarian could have chosen to believe in determinism. In both cases, the agent chose their belief. In choosing their belief, they can choose to defend their belief or change their belief.

The process in which an agent's conclusion is reached is through reasoning. There are many factors that are involved (environment, circumstances, thoughts that pop into your mind out of "nowhere") but those factors are included in the reasoning process.

The reasoning process involves the agent actively evaluating said factors (described previously) to then come up with a motivation for their intent.
Intent is formed and that intent guides the agent's actions.

The agent has effectively started a new causal chain in which a series of events will proceed. If the agent does not proceed, this will also be their choice with a different set of reasons as to why.

Ultimately, the existence of the debate itself serves as evidence for the agent's autonomy. Whether one concludes in favor of free will or determinism, that conclusion is not just a byproduct of biology, but a deliberate architecture of thought. By evaluating evidence and committing to a stance, the agent does more than react to the world, they author their place within it.

To argue against free will is, ironically, to exercise the very capacity for independent judgment that the denier seeks to disprove. Thus, every reasoned defense is not just a statement of belief, but the first link in a brand new chain of causality, forged by the agent alone.

The "I feel free" argument is weak. Subjective experience is messy, and any neuroscientist will tell you your brain is just a series of electrical impulses you don’t control. Most people get stuck wondering if they feel free. That’s a trap. Instead, look at the Preconditions of Reason.

You can't argue against free will without accidentally proving it exists. Here’s why.

1. The "Calculator" Problem

To truly know something, you have to evaluate evidence against logical rules and decide it’s true.
Think about a calculator. When it spits out 2 + 2 = 4, it doesn’t "know" anything. It’s just a physical system where an input (pressing buttons) leads to an inevitable output (the screen lighting up) based on its wiring. It can’t "choose" to be wrong, so it can’t "know" it’s right.

If your thoughts are 100% determined by your brain chemistry and prior causes, you aren't "reasoning"—you’re just reacting. You didn't "reach" a conclusion; you were physically compelled to arrive at it.

2. Determinism is a Performative Contradiction

The moment someone says, "I’ve concluded that free will is an illusion," they’ve walked into a logical trap.

If their conclusion was determined by their neurobiology before the conversation even started, they didn't actually "evaluate" anything. They’re just a set of gears turning. You cannot claim a belief is "rationally justified" if you were physically forced to believe it. It’s just a byproduct of your biology, like a sneeze or a heartbeat. You don't "justify" a sneeze; it just happens.

3. Argumentation as Proof

The very act of debating someone presupposes two things:

1. You have the agency to choose the better argument.

2. Your opponent has the agency to be persuaded by logic.

If we were all strictly determined, "persuasion" wouldn't exist. We’d just be waiting for our internal programming to update. To argue against free will is to treat your opponent like a free agent capable of changing their mind based on merit—which is exactly what you're trying to say they can't do.

Free will isn't a "vibe" or a religious mystery; it’s a logical necessity.

Without the ability to freely choose between ideas based on their merit, "truth" isn't a rational discovery—it's just a mechanical byproduct. If we can reason, we must be free. If we aren't free, then we can't trust a single thought in our heads, including the thought that we aren't free.

If you’re using logic to argue against free will, you’re using the very thing you’re trying to disprove. You’re trying to saw off the branch you’re currently sitting on.