Hard determinism holds that determinism is true and that free will requires incompatibilist freedom, which doesn't exist — therefore no one is ever truly free or morally responsible in the basic desert sense. Hard incompatibilism (Pereboom) extends this: even if indeterminism is true, it doesn't rescue the kind of control needed for basic desert responsibility. The position has radical implications for moral practice — retributive punishment cannot be justified, though consequentialist practices of behavior modification, rehabilitation, and incapacitation might be. Proponents argue we should revise, not deny, our reactive attitudes.
Read Pereboom's Living Without Free Will, especially the four-case manipulation argument and his account of how we should revise our reactive practices. Evaluate whether the revision he proposes is psychologically and practically coherent.
From your study of free will and determinism, you already understand the basic incompatibilist argument: if every event is determined by prior causes plus the laws of nature, then human actions are also so determined, and no one could ever do otherwise than they do. Hard determinism accepts this argument and draws the full consequence: since free will (in the sense incompatibilism requires) does not exist, and moral responsibility requires free will, no one is ever truly morally responsible in the basic desert sense — meaning no one deserves praise or blame in the way that would justify retributive responses.
The more sophisticated position developed by Derk Pereboom is hard incompatibilism, which is important because it doesn't depend on determinism being true. The worry about indeterminism is that it doesn't obviously help: if my action is partly the result of random quantum events in my neurons, those events are *mine* in no meaningful sense either. They don't give me the authorship or control that robust moral responsibility requires. So whether the world is deterministic or indeterministic, the kind of free will required for basic desert — where the agent is the *ultimate source* of her actions in a way that's not reducible to prior causes or chance — seems unavailable. Hard incompatibilism holds that this conclusion follows regardless of what physics ultimately shows.
The most powerful argument for this view is Pereboom's four-case manipulation argument. He describes four scenarios involving an agent named Plum who kills someone. In case one, Plum's action is entirely controlled by neuroscientists who directly manipulate his brain states. In case four, Plum acts through an ordinary deterministic causal history. The cases form a continuum: each intermediate case involves slightly less direct external manipulation and slightly more "normal" internal causation. Pereboom argues that since Plum clearly isn't responsible in case one, and since there is no principled distinction between the cases that would ground responsibility reappearing at case four, Plum isn't responsible in the ordinary deterministic case either. The argument challenges you to find where exactly responsibility enters — and if you can't, the conclusion follows.
The most practically significant implication is for punishment. If no one deserves punishment in the retributive sense, then the entire structure of criminal justice built around giving people what they deserve collapses. Hard incompatibilists like Pereboom don't conclude that we should release everyone from prison; they argue instead for a forward-looking, consequentialist justification of state responses to harmful behavior. Incapacitating dangerous people, rehabilitating offenders, and deterring future harm can all be justified without appealing to desert. What disappears is the idea that suffering is intrinsically appropriate as a response to wrong-doing.
Crucially, this view does not erase the distinction between voluntary and coerced action, or between the neurotypical and the severely mentally ill. Those distinctions matter for causal and predictive reasons — voluntary actions better predict future behavior, rehabilitation is more feasible in some cases than others. What hard incompatibilism denies is that these distinctions ground *desert*-based responses. The practical reforms in our reactive attitudes — in how we feel anger, resentment, and indignation — are more profound than the institutional reforms, and Pereboom takes seriously the question of whether revision of these deep emotional responses is psychologically achievable.
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