Neither in the sky nor in mid-ocean,
nor in a mountain cave,
is found that place on earth
where one may escape from karma.—Dhammapada
Some might concede that free will and souls are impossible in the physical world, governed as it is by the deterministic-probabilistic laws of quantum mechanics, but maintain that souls exist in a spiritual realm not subject to physical laws. This chapter examines and refutes this possibility.
Theorem 4.1 (Free Will Impossible in Any Realm). Free will is impossible in any realm—physical, spiritual, or otherwise.
Proof. The argument of Chapter 1 does not depend on the specific laws of physics. It depends only on the logical exhaustion of possibilities: any event is either determined by prior causes, or not; if not, it is to that extent random.
Consider a spiritual realm with its own “spiritual laws.” For any event \(E\) in this realm, either:
\(E\) is determined by prior spiritual states according to spiritual laws (spiritual determinism), or
\(E\) is not so determined (spiritual randomness), or
Some combination of (1) and (2).
By the same arguments as Theorems 1.1, 1.2, and 1.3, none of these possibilities permits free will. The argument is completely general and applies to any conceivable realm.40 ◻
Corollary 4.2 (No Spiritual Souls). If souls require free will, and free will is impossible in any realm, then souls are impossible in any realm.
Even setting aside the free will problem, positing spiritual souls faces the interaction problem: how could a non-physical soul interact with a physical body?41
Theorem 4.3 (Causal Closure of Physics). If physics is causally closed (every physical event has a sufficient physical cause), then non-physical souls cannot causally influence physical events.
Proof. Suppose physics is causally closed: for every physical event \(P\), there is a sufficient physical cause \(P'\).
Suppose a non-physical soul \(S\) causes a physical event \(P\) (e.g., a neural firing that initiates a bodily movement).
By causal closure, \(P\) has a sufficient physical cause \(P'\).
If \(P'\) is sufficient for \(P\), and \(S\) also causes \(P\), then either:
\(S\)’s causation is redundant (overdetermination), or
\(S\) acts by influencing \(P'\) (but then \(S\) causes a physical event \(P'\), regenerating the problem), or
\(S\) acts by modifying the laws that connect \(P'\) to \(P\) (but then the laws are not fixed, contradicting the assumption of physical law).
Option (1) makes \(S\) causally inert for all practical purposes. Options (2) and (3) either regenerate the problem or violate physical law. Therefore, \(S\) cannot causally influence physical events without violating causal closure. ◻
Remark 4.4. Modern physics provides strong evidence for causal closure. The Standard Model of particle physics, combined with general relativity, accounts for all known forces and interactions. There are no “gaps” where non-physical causes could intervene without showing up as violations of conservation laws (energy, momentum, etc.) that have been confirmed to extraordinary precision.42
We now show that even if a spiritual realm existed, souls in that realm would require free will—and free will, as shown, is impossible.
Theorem 4.5 (Functional Requirement of Free Will for Souls). For a soul to serve its traditional functions (moral responsibility, desert of reward/punishment, personal identity through time, survival of death), it must possess free will.
Proof. Consider each function:
Moral responsibility: To be morally responsible for an action, one must be the originating source of that action, not merely a conduit for prior causes or a locus of random events. This requires free will.43
Desert of reward/punishment: To deserve reward for a good deed, one must have freely chosen to perform it when one could have done otherwise. If the deed was determined or random, there is no merit in it—it would have occurred regardless of any choice. Similarly for punishment: punishing someone for an action they could not have avoided is unjust.
Personal identity: If the soul is subject to determinism, then its states at any time are fixed by prior states, and there is no “self” doing anything—just a sequence of states following a causal law. If subject to randomness, the “self” is a series of disconnected random events with no unifying agent. Either way, the robust personal identity that souls are supposed to provide dissolves.
Survival of death: Even if something survives death, if it lacks free will, it is not an agent that survives but merely a process that continues. The religious significance of survival (judgment, reward, punishment, reunion with loved ones, etc.) depends on the survivor being the same person who lived, with agency and responsibility intact. A deterministic or random survivor would not be the same person in the morally relevant sense. ◻
Corollary 4.6. Souls, to fulfill their traditional functions, require free will. Since free will is impossible in any realm, souls cannot fulfill their traditional functions in any realm. Therefore, the concept of “soul” as traditionally understood is incoherent.44