Sunday, March 18, 2018

Mental States are Causally Irrelevant on Naturalism (p. 2)

Home > Philosophy > Metaphysics
  1. Problems for Naturalism
  2. Why Mental States are Causally Irrelevant on Naturalism
  3. The Symbolic Logic
  4. Proving It
  5. The Argument is Sound, but So What?

Why Mental States are Causally Irrelevant on Naturalism



The reason why mental states are causally irrelevant on naturalism is actually pretty simple. Say that initial physical conditions are the initial conditions as specified in the domain of physics (types of particles, number of particles, their arrangement, etc.), that laws describe how the physical stuff (in the domain of physics) behaves in the absence of supernatural intervention including specifying the physical outcome of what will happen (e.g. where certain particles end up) given certain initial physical conditions in the absence of supernatural intervention[2], and that a physical state is the initial physical conditions and the laws that govern them.

Insofar as chemistry is reducible to physics (in that chemistry describes how certain combinations of the entities in physics behave with each other; e.g. how molecules interact with other molecules) the laws will consequently include the laws of chemistry. Insofar as biological systems like amoebas are merely very complex combinations of the entities of physics including molecules, those biological systems will include systems of chemistry and physics.

Now consider the following thought experiment: suppose on naturalism a given physical state (one that consisted of one person or many persons in the universe) were to have an entirely different set of mental states associated with this same physical state. Would the outcome be any different? It would not, because the same physical state means the same initial physical conditions and the same laws, so by definition we would get the same physical outcome in the absence of any supernatural intervention to change how things would go. On naturalism, if a different mental state (or no mental states) were associated with a given physical state, we’d get the same physical outcome (e.g. the same behavior) and on naturalism mental states are causally irrelevant in the sense that it doesn’t matter which mental state (if any) is associated with a given physical state; we’d still get the same physical outcome. We can structure this reasoning with the following argument:
  1. On naturalism, the following is true: If a physical state had any different set of mental states associated with it, the same outcome in the physical world (e.g. one’s behavior) would result.
  2. If (1) is true, then mental states are causally irrelevant on naturalism.
  3. Therefore (On naturalism), mental states are causally irrelevant.
Justification for (1): Physical states comprise of the initial physical condition and the laws that, by definition, say which physical outcome will occur given those initial physical conditions in the absence of supernatural intervention. Consequently, it would be self-contradictory on naturalism (which says there is no supernatural intervention) to have the same physical state (i.e. same initial physical conditions and the same laws) but a different physical outcome. So on naturalism, if a different set of mental states were associated with the same physical state, the same physical outcome would result.

Justification for (2): By “mental states are causally irrelevant” I mean in the sense that in the sense that it doesn’t matter which mental states the physical processes generate, and it doesn’t matter which set of mental states (even an empty set) is associated with the physical state of the world: it wouldn’t change the physical outcome (e.g. the same behavior would result). So essentially (2) is true by definition by what I mean by “mental states are causally irrelevant.”

I suspect this sort of argument would convince most people (and if you’re already convinced, maybe you want to stop here). But some people (probably naturalists) can be remarkably resistant to the idea that mental states are causally irrelevant on naturalism. Fortunately, we can use the power of symbolic logic to help prove that mental states are causally irrelevant if naturalism were true. First, I’ll introduce some symbolic logic before giving the formal proof in symbolic logic.

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[2] What if the outcome is random, such that (for example) there is exactly a 50% chance of a certain particle undergoing radioactive decay within a specified time period? In that case, the “outcome” would be something like “there is a 50% random chance that the particle undergoing radioactive decay within that time period such that on average, it will (randomly) decay 50% of the time.”

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