Word of the Week: Compatibilism

 Portrait of compatibilist Immanuel Kant

Note: key words or phrases coloured in orange constitute the unfettered determinism that Kant is opposing, whilst everything coloured in purple constitutes the theory that Kant is advocating - namely, compatibilism. 

Last week, I asked whether determinism, or the theory that humans have no free will, is convincing. This week, I consider whether compatibilism, or the view that free will and the rigid laws of nature are compatible, is reasonable. There are a range of compatibilist thinkers out there, but today I'll focus on one of the the most convincing compatibilists - Immanuel Kant. In his Critique of Pure Reason, his Grounding for the Metaphysics of Morals, and his Critique of Practical Reason, Kant suggests that determinism may have an element of truth. But he also provides two arguments against unfettered determinism and for compatibilist free will. Kant thus occupies a middle ground between advocates of complete free will and hard determinists. 

Firstly, Kant argues that the ‘autonomy of the will’ is the ‘supreme principle of morality’. Determinists would like to argue that the will is heteronomous, or that the will, when making judgements, always looks to the ‘objects of volition’, or desires such as egoism and concern about one’s reputation. However, Kant argues that the will is actually autonomous: when we say ‘I ought not to lie’, even the most committed villain would not assert that this ‘ought’ entails the condition that ‘I would maintain my reputation’. Therefore, any imperative, Kant asserts, is not hypothetical, but is rather categorical. In more common language: an imperative is absolute and not relative to the situation. So the will should not look to sentiments in reaction to the external world, but rather to the reason given to us by our internal mind. As our moral will is created internally rather than externally, and is autonomous rather than heteronomous, Kant insists that the will is free. John Locke and David Hume used similar arguments in their emphasis on internal rather than external causes as the key determinants of the will. For compatibilists, therefore, our will is both free and determined: we lack ‘external impediments’, and in that sense are free, but still have to listen to the internal maxim of the categorical imperative. Here is my formal presentation of Kant's argument, using my own logic:

1. If determinism rules out free will, then the will is not free;
2. If the will is not free, then it is heteronomous;
3. If the will is heteronomous, then it is not autonomous;
4. If the will is not autonomous, then moral imperatives are hypothetical (relative);
5. If moral imperatives are hypothetical, then they are not categorical (absolute);
6. But moral imperatives are categorical, e.g. 'I ought not to lie';
7. Therefore, moral imperatives are not hypothetical;
8. Therefore, the will is autonomous;
9. Therefore, the will is free, i.e. free will exists;
10. Therefore, determinism does not rule out free will.

However, this suggests that the will is always categorical, when in fact people are perfectly capable of willing something with reference to a multitude of external, sentimental causes. Examples of non-moral (i.e. non-categorical) causes include the enhancement of one’s reputation instead of the adherence to a Kantian ‘universal law’. So internal and external causes, together with rational and sentimental causes, are not clearly distinguishable, suggesting that compatibilism may be misled. Kant relies on the autonomy of the will to justify the categorical imperative and, in turn, free will.

The second Kantian argument for free will worth noting is his ‘third antimony’ found in the Transcendental Dialectic (from Kant's Critique of Pure Reason). Kant contrasts free will and determinism by analysing the arguments for both. On the one hand, Kant acknowledges that free will gives humans control over their actions, but on the other hand Kant admits that all objects presented to our senses are predetermined, including human action and the will. However, here Kant refers back to the distinction he made in the Transcendental Aesthetic between the noumenal world (or the real world) and the phenomenal world (or the apparent world). Whilst all objects occupying space and time are part of the phenomenal world, Kant suggests that space and time are just subjective intuitions. Thus the noumenal (real) world may not really be that which we perceive when we see, touch, smell, taste or hear objects. Instead, the noumenal world lies beyond our senses, and is thus totally unknowable, since Kant agrees with the empiricists that we cannot prove, metaphysically, the existence of anything without referring to our senses. Although Kant disagreed with Newton on many issues (such as the very noumenal existence of space and time, which Kant denied and Newton affirmed), they agreed that experience is the limit of our knowledge concerning what seems to exist. So Kant said that, whilst determinism is a property of the phenomenal world, free will may be a property of the noumenal world. Here I use Leibnizian logical laws to explain Kant's point:

1. According to Gottfried Leibniz's Indiscernibility of Identicals, if x is identical to y, then for every property F, object x has F if and only if object y has F; i.e.  x=y → ∀F(Fx ↔ Fy); 
2. Therefore, if we let p equal the phenomenal world and n the noumenal world, then n=p implies that for every property D, or unfettered deterministic causation without a jot of free will, n has D if and only if p has D; i.e. n=p → ∀D(Dn ↔ Dp).
3. According to Leibniz's Identity of Indiscernibles, if, for every property F, object x has F if and only if object y has F, then x=y; i.e. ∀F(Fx ↔ Fy) → x=y;
4. But we can never describe space or time in concrete terms, but only in incomplete analogies such as 'time [is] a line progressing ad infinitum' (Critique of Pure Reason, 1781); this is an incomplete analogy because, whilst the parts of a line are simultaneous, time occurs sequentially; in other words, whilst it is true that our intuitions of space and time are properties of the phenomenal world, it is not necessarily true that intuitions of space and time are properties of the noumenal world. So, where the logical symbol '¬☐' means 'not necessarily' and the property I means 'our intuitions of space and time', it's not necessarily true that our intuitions are properties of the noumenal world; i.e. ¬☐{∀I(In ↔ Ip)};
5. Therefore, and with reference to Leibniz's Identity of Indiscernibles, it is not necessarily true that the noumenal world is identical to the noumenal world; i.e. ¬☐{∀I(In ↔ Ip)} → ¬☐(n=p);
6. Therefore, and with reference to Leibniz's Indiscernibility of Identicals, it is not necessarily true that deterministic causation without any free will is a property of both the noumenal and phenomenal world; in other words, merely phenomenal determinism does not preclude noumenal free will; i.e. ¬☐{∀D(Dn ↔ Dp)}.

However, this argument can be criticised using Kant’s original assertion in the Transcendental Aesthetic—namely, that the noumenal world is unknowable. As such, whilst determinism is at least a property of one of these worlds (the phenomenal world), we can never say for certain whether free will is a property of any world (the phenomenal world or the noumenal world). Determinism is, in all probability, more ‘real’ than free will, such that Kant’s compatibilist balance between free will and deterministic causation cannot, realistically, be exactly 50:50.

Overall, whether you accept Kantian compatibilism rests on whether you accept the possibility of categorical imperatives, as well as the possibility of any speculation at all regarding the noumenal world. The choice is yours... or is it?

Disclaimer: Kant is notorious for the myriad of possible ways of viewing his work. So this post gives my personal interpretation of Kant's work, which I leave open to debate amongst Kant scholars with different interpretations and other students of the revolutionary Königsberg philosopher. This is, after all, what Kant said 'enlightenment' was all about.