Building Blocks for the Critique of Pure Reason: experience and necessity.

 

The fact that we have knowledge of truths that are both necessary and universal is one of the most basic building blocks of the CPR. Indeed, Kant draws attention to it in the first paragraph of the Introduction:

Experience is without doubt the first product that our understanding brings forth as it works on the raw material of sensible sensations. It is for this very reason the first teaching, and in its progress it is so inexhaustible in new instruction that the chain of life in all future generations will never have any lack of new information that can be gathered on this terrain. Nevertheless it is far from the only field to which our understanding can be restricted. It tells us, to be sure, what is, but never that it must be so and not otherwise. For that very reason it gives no true universality, and reason, which is so dersirous of this kind of cognitions, which at the same time have the character of inner necessity, must be clear and certain for themselves, independently of experience; hence one calls them a priori cognitions: whereas that which is merely borrowed from experience is, as it is put, cognized a posteriori, or empirically.

We can extract three key claims from this quote:

1. Experience is without doubt the first product that our understanding brings forth as it works on the raw material of sensible sensations. Note the implications of this sentence: experience is a product of work done by our understanding, not something given which our understanding goes to work on. If anything is given it is ‘the raw material of sensible sensations’, and Kant is careful, even at this early stage, to distinguish this from ‘experience’ in the full and proper sense. More on this in a separate post. The key point here is that, temporally speaking, experience is our first source of knowledge: we continually learn things from our interaction with the world, a process which could potentially go on interminably, so rich is the field of experience.
2. Nevertheless it is far from the only field to which our understanding can be restricted. So experience is not the only possible source of knowledge, even it is the first (again, because this will be important, the first in temporal terms). Already Kant is differentiating his work from that of the Empiricists – philosophers such as Locke, Berkeley, and Hume – who argued that all knowledge has its basis in experience. Kant allows that experience is a reliable – indeed inexhaustible – source of knowledge, but it is not the only one
3. It [i.e. experience] tells us, to be sure, what is, but never that it must be so and not otherwise. Now the most important point: experience can tell me that such-and-such is the case – that my cup of tea is almost full, that my friend is fond of American detective novels, that Alaskan Bar-tailed Godwits have the longest non-stop flight of any migrating bird – but it cannot tell me that such-and-such must be so and could not be otherwise (a determinist might state that these truths were necessary, but this requires further argument, and it not apparent from the experiences themselves). In other words, experience provides us with a particular type of knowledge.

We can draw out three charasteristics of this type of knowledge. Either, such-and-such is the case, but it could have been otherwise, i.e. it is contingently true. For example, my cup of tea may be almost full, but this is not necessarily so – I could have drank most of it before sitting down to write; I could have made a cup of coffee instead; I could have no drink at all. Or, such-and-such is the case, but it is not universally true – again, although my cup of tea was almost full when I wrote the previous paragraph, it is now almost empty; alternatively, my friend may be fond of American detective novels at the moment, but there was a time when he had never read one, and possibly he will grow tired of them one day. Or, such-and-such is the case, but is subject of falsification based on another possible experience – it may in fact be true that the Bar-Tailed Godwit makes the longest flight of any migrating bird, but possibly we could have some experience which would show us that this is not the case – the discovery of a new species of bird, or a change in migratory patterns. Let it be clear that we are not challenging the characterisation of these pieces of knowledge as truths, or even as genuine examples of knowledge. Rather we are drawing attention to particular facts about the nature of such knowledge.

Importantly, not all knowledge is of this sort. We know some things which are not only true, but which could not be otherwise: that 7 + 5 = 12, for example. More controversially, that every effect has a cause, or certain facts about the nature and structure of space and time. For ease of exposition, I will use mathematical truths in all the following examples – hopefully I’ll get round to talking about the relative status of mathematical and other truths with regard to universality and necessity in later posts.

These truths, though they may have their origin in experience, cannot rely on it for their justification. They fail to meet the three criteria we established for such truths: they are not contingent (whatever the prior and future history of the world, it is always true that 7 + 5 = 12); they are universal, not specific or singular (it is always and everywhere true that 7 + 5 = 12); they are not subject fo falsification by experience (there is no possible experience which would lead us to conclude that it is not true that 7 + 5 = 12 – once one understands that this is true, it is impossible to imagine it being otherwise).

Because of these features, our knowledge of such truths cannot be justified by experience. And yet we do undoubtebly have knowledge of them. This is the first building block in Kant’s argument.

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