In philosophy, one of the most (in)famous thoughts is that of Kant's concerning the "thing in itself." This "thing" is something which exists beyond our perception of objects. Now, many thinkers attribute to Kant the view that the thing in itself is "unknowable." However, "knowing" in the context of the Critique of Pure Reason has a very precise meaning, namely, that of becoming an object for cognition. The thing in itself is, according to Kant, something which is not incorporated into the result of our cognitive activity. Therefore, while we do "know" certain things about the thing in itself - that it is beyond cognition proper, that it nevertheless exists "out there" etc. - we cannot examine it and ascertain its qualities. In Kantian jargon, another way of putting this is to say that the thing in itself is empirically unknowable but transcendentally knowable. The message here is the same: the thing in itself cannot be subjected to direct observation, and as such we cannot ever receive its specific determinations.
It is also a curious fact that Kant very often designates the thing in itself in the plural form: noumena, or "things in themselves." This suggests that what is beyond our cognitive capacities is diverse, within which distinctions are already made. But why would this be the case? Is this not already "applying" human concepts onto things which, as Kant claims, cannot be grasped in human terms? This is the first criticism of Kant's thought concerning the thing in itself.
The second criticism, which is really the other side of the first, is often entertained by the post-Kantian idealists such as Fichte, Schelling, and Hegel. Here, instead of criticizing Kant for introducing a determination to something which is supposed to be "unknowable," the critics accuse Kant of not going far enough in determining the thing in itself. According to this view, to say that things in themselves are diverse is an idleness of the intellect in not being able to speculate further. If we are able to claim that the thing in itself exists, and if we are able to think of it as a plurality or as a singularity, then it must be possible to think it in all sorts of other ways. All of these thoughts ought to be examined systematically, so that, while we may not have empirical access to it, the thing in itself may nevertheless be revealed to us in all of its possible determinations.
Hegel in particular carried out this second criticism both implicitly and explicitly in his own system. The Science of Logic, as the science of thought, is essentially a gigantic work on the various possible determinations of the thing in itself. For Hegel, it is not the thing in itself per se that is problematic in Kant, but rather its status as a "pure beyond," which amounts to a null object devoid of significance. Hegel already finds the germ of both positions in Kant: on the one hand, the Kant of the Transcendental Dialectic gives a positive account of the thing in itself, claiming that it is that which we are able to think it is, while, on the other hand, the Kant of the Transcendental Analytic shrinks back into skepticism, claiming that the thing in itself is merely the beyond of cognition.
For Hegel, the ways in which empirical objects appear to us each presuppose how we think about - either implicitly or explicitly - the thing in itself. To give a simple example also often used by Kant, consider a criminal in a court hearing. The accuser might state the criminal's personal tendencies which, arising out of the freedom of the criminal himself, conditioned and led to the crime. The defendant, on the other hand, might point to the natural upbringing of the criminal, and how this made the crime inevitable or necessary. The former attitude attributes responsibility to the criminal himself, while the latter attitude does not. In order to decide the truth of either position, one only needs to examine how both presuppose a different thought concerning the thing in itself, namely, the criminal. There is nothing empirical in either the claim to freedom or to necessity. In other words, we cannot simply observe the criminal as in our observations of animals in zoology or of particles in physics, and from this observation draw an inference in favor of one or the other. Rather, in order to observe the person as free or determined, we need to presuppose a certain thought concerning what he is supposed to be in the first place. Hegel's claim is that we make such presuppositions all the time, and there is no escape from them.
Here I would like to introduce a third figure into this debate: David Hume. Hume's position is very close to Hegel's, or rather, the latter's is close to the former's. Hume famously claimed that the idea of causality is not the property of the object - Hume's term for the thing in itself - but rather is something which we infer from our perceptions. However, Hume also recognizes, and elaborates on the view, that causality is necessary and essential to how we interact with objects and with each other in our everyday lives. It is only when we abstract from our everyday immersion with things and take the philosophical attitude that we come to see that causality is not "in" the object. For Hume, skepticism is thus the necessary outcome of taking the philosophical stance, while naturalism, or more precisely a kind of projectionism, is the inevitable result of coming back to our everyday practical perspective.
Now in his Treatise of Human Nature Hume elaborates on this general train of thought and applies it to other ideas too such as identity, substance, accident, matter, solidity, etc. In each case, Hume shows that these are not determinations of the object, but rather ideas which we infer from our perceptions and then project back onto the external world. These ideas, however, are indispensable to our practical affairs. Thus, the practical attitude demands that we take objects to be constant, exist outside perception, and have a necessary causal connection with each other. A bread will cause calories to be transferred into our bodies. A word of insult will cause anger or sorrow in the mind of our friends. There are a million such suppositions which we unconsciously entertain on a daily basis. It is only by shifting our position, and thus adjusting our thoughts, in a properly philosophical way that we are able to take the skeptical standpoint and recognize this as expressing the truth of things.
Hume here highlights the irresolvable tension which exists between the practical, everyday attitude and the theoretical, philosophical one. In so far as this tension goes, Hume is here very close to Kant. However, Hume is close to Hegel with regards to his account concerning our ideas which we project onto things in themselves. Unlike Kant, Hume is explicit in his claim that all sentient beings necessarily project these ideas onto things which go beyond their perception. Hume has a nice account of why this is necessary from a practical point of view. The name Hume gives to this necessity is "habit" or "custom," and it is supposed to be a tendency which we carry within ourselves from our birth. It is "a priori," to put it in Kantian jargon. Thus, the thing in itself vanishes out of sight the moment we adopt the practical attitude. On the other hand, objects, as things beyond our cognition, become accessible to our thoughts as they are - namely, as things which simply are beyond our capacity to grasp them - from a theoretical standpoint. Perhaps here is the point at which Hume and Hegel differ. For Hegel, it might be claimed that the various determinations of the thing in itself come into view from a purely philosophical point of view. Whereas for Hume, the practical stance is a necessary per-requisite for us to spontaneously infer certain determinations concerning objects, and then, by criticizing these inferences reflectively, we finally come to see retrospectively how we determined the thing in itself. Here, the alteration between practice and theory is necessary for us to fully grasp how we think about the thing in itself.
After this comparison, it is evident how the three thinkers made their own respective contributions towards an adequate concept of the "beyond" of cognition. Kant gave it the most appropriate name, the thing in itself. Hume pointed out the perspectival shift which necessarily precedes any positive account concerning the thing in itself. Hegel provided an extensive thought-map for understanding the possible determinations which we may give to the thing in itself. These thinkers often misinterpret each other with regards to this issue of the beyond. But a close and generous comparison reveals a possible way to combine their respective accounts into a coherent new theory. Admittedly, the present interpretation is no more than a suggestion which, for the moment, must await further development.
