For any who don't know, determinism (Easy Mode, Hard Mode) is the idea that the entire Universe - humanity included - is on causal rails. As a consequence, there can be no such thing as free will - as compelling an illusion as it is, it is still merely an illusion. The three positions surrounding the issue of free will can all be derived from an inconsistent triad (an inconsistent triad is a set of three common-sense propositions which can't all be true), viz:
1. People have free will.If one rejects 1, then one is a determinist; if one rejects 2, then one is a libertarian (philosophical libertarianism is distinct from political libertarianism); if one rejects 3, then one is a compatibilist. It bears mentioning that compatibilism is at least a little bit silly, because it typically involves redefining "free will" such that 3 is manifestly false; as a consequence, the libertarian's meaning of "free will" is not preserved, and so the libertarian's meaning of 1 is covertly rejected. In other words, compatibilists are determinists in disguise who want to preserve the phrase "free will" in the common parlance, robbed of its philosophical force.
2. Causality regulates the entire Universe.
3. If people have free will, they must somehow defy causality (i.e. "1 and 2 cannot both be true").
At any rate, the problem of moral responsibility is at least respectable on its face: it doesn't really make sense to blame or punish someone for something if they were unable to do otherwise, and determinism definitely holds that "for any action that a person has taken, that person was unable to do otherwise." That's a consequence of being on causal rails. However, as I intend to show, determinism not only fails to make moral responsibility incoherent, it actually encourages a more humane theory of justice when properly understood.
So, without further ado, let's play Slippery Slope!
Our first order of business shall be to lay out some starting premises:
A) Justice, essentially, is the idea of "people getting what they deserve."The particular phrasing of the above is not designed for precision, but rather to foster agreement. For instance, A is not exhaustive - justice may mean "rewarding good and punishing evil," but these rewards and punishments are deserved - so, no matter the details of your theory of justice, I think that we all (myself and you, the General Reader), can agree that the "core" or "essence" of justice is "people getting what they deserve," while exactly what is deserved may remain at issue for another discussion.
B) Generally, justice is desirable - we want people to get what they deserve.
C) There is such a thing as "causality."
D) Because of C, we can talk coherently about causal sequences (or "causal chains").
E) Because of D, we can meaningfully distinguish between types of causes (e.g. "sole causes" vs. "partial causes," "immediate causes" vs. "root causes," etc.).
F) There are also chains of moral responsibility - no matter your ethical system, if there is moral responsibility at all, it must follow some kind of chain, from the moral status of the event back to whatever it is that is morally responsible for that event.
G) Moral chains and causal chains are not identical, but moral chains must overlap causal chains.
H) Corollary to G is its converse: there can be no chain of moral responsibility where no chain of causal responsibility exists (in other words, one is not morally responsible for that which one does nothing to cause).
I) Determinism at least seems to take the edge off of justice.
So far, we all ought to be able to agree that justice is a desirable thing, it needs chains of moral responsibility upon which to operate, and these moral chains have to "stick to" causal chains which can get complicated. Given that, let us imagine that Bert hypnotizes Ernie, and as a result of this hypnosis, Ernie becomes a serial murderer; Ernie's first victim is Big Bird. Big Bird's murder is a morally bad act, to be sure, and we can see that Ernie is the immediate cause of it (well, the method of murder is technically the immediate cause, but whatever). But, since we understand that Ernie only murdered Big Bird because Bert hypnotized him into becoming a murderer, we can see that the causal chain extends through Ernie back to Bert. I think we can all agree that the moral chain also goes back to Bert, but in order to do so, it must go through Ernie.
This puts Ernie in an interesting position: neither the causal nor the moral chain has its source in Ernie, yet Ernie committed the murder itself and is thus inextricably involved. And, per my stipulations, Ernie will kill again unless we do something about the causal antecedents which precipitated Ernie's actions. In short, and obviously, Ernie's hypnosis should be cured - we don't want him to keep running around killing people, do we? Moreover, I think Ernie deserves to have his hypnosis cured, which makes curing him a just action. While it is too late by far to give Big Bird what he deserves, we can still do justice to Ernie by curing his hypnosis. Obviously, something needs to be done about Bert and his hypnotic method as well, since the creation of murderers tends to be detrimental to society.
Let's leave Bert aside for the moment. The situation we're looking at is thus: Ernie engaged in a problem behavior, even though the problem behavior was out of his control, and in order to do justice to Ernie, we are proposing to address the cause of the problem behavior so that it will no longer be a problem. Furthermore, we are also proposing to take broader actions to prevent the same cause of Ernie's problem behavior from causing similar problem behaviors in others, even though such problem behaviors would not ultimately be the fault of those who fell victim to this cause. This is humane, good, and just.
This is also a deterministic model of justice. Anyone who proposed that Ernie must be punished rather than merely cured would reveal himself for a sadist, since punishing Ernie is not necessary to solve the problem at hand. If, as in the real world, it turned out that we could only (or even most likely) prevent problem behaviors in Ernie by punishing him, then punishment would be an option on the table - but our focus should be on solving the problem, not on administering punishment. And so, in the real world, our justice system ought to be focused primarily on solving the problems that cause people to harm others. Punishment certainly can facilitate this, and so ought not to be rejected out of hand, but it also should not be pursued as if it is good by itself, or even necessary for justice to occur. Those who would advocate punishment when it is not necessary are, consequently, asking for unnecessary harm to come to an individual - seemingly for its own sake. And wishing harm upon others for no good reason is a well-respected definition of sadism, which most certainly is not justice.
There's even a snappy common-sense angle to take on this. Empathy is a good thing, as it inspires people to treat others how they would like to be treated themselves. Those who think it is OK to harm others must clearly have a problem with their empathy (those who harm others solely out of ignorance merely need to be educated). This means that there's something wrong with them, that their "moral sense" is somehow inadequate at the moment. So - and here's the snappy part - if these people have something wrong with them, how is harming them supposed to improve things?
A deterministic model of justice, as we have seen, naturally encourages a more humane criminal justice system, and exposes the sadism in retributive justice for what it is. Retributive justice should only be used when necessary, and should not be relished, but does not conflict with a deterministic worldview (visible retributive justice can still generate perfectly deterministic deterrence, for example). There is no inherent conflict, therefore, between determinism and justice, so the apparent problem mentioned above in I turns out to be illusory.