Earlier I discussed Aristotle’s senses of before and after. Using yesterday’s discussion of one and many, we can now find a more exact definition of the same terms.
We can define “second” as the formal part of something two, namely the part by which the two is two.
Thus “first” is the part of something two which is not the second. This way of defining first and second may seem backwards, but it is analogous with how we defined the unity of a thing by negating division.
Something first, as such, implies the existence of something second, and likewise something second implies the existence of something first. However, the existence of two implies the existence of one (as a part), while the existence of one does not imply the existence of two. This corresponds to the difference in the definitions of first and second given above. The second is the part by which two is two, while the first is a part, but not the part by which two is two. If first and second are considered only with respect to what is formal in them, then, as “not that by which two is two”, and “by which two is two”, then according to this consideration the first does not imply a second, but the second implies a first.
From this we can see that being before by nature, or as Aristotle says, “what does not reciprocate according to consequence of being,” if not the first thing to which the words before and after are applied, is nonetheless first in the nature of things to possess the before and after.
We can also see that this sense of before and after must be found in some way in all other senses, for every case of before and after will involve something first and something second.
This can be illustrated with the order of time, the first thing to which the words before and after are actually applied. At first it might seem that such a before and after are completely separate from the idea of reciprocation according to consequence of being, since one day can exist without another, nor is it evident that the existence of one day implies that another day existed or that another will exist.
If we consider our actual experience of the past and present (since we have no experience of the future), however, we find something different. Our experience of the present includes our memory of the past, and in this respect implies the past existence of the past. But our experience of the past, namely not the present experience of remembering the past, but the remembered experience of the past that was once present, does not include anything of the present. In this way the present implies the past, but the past does not imply the present, and thus according to these considerations the past is before the present even according to consequence of being.
This is not to deny that according to other considerations the present might be before the past. Rather, these considerations show why the past is considered to be before the present, namely because the present seems to build on the past, as though the past were one block of wood, with the present being a second block of wood stacked on top of the first block. We will find that something similar is the case in every way in which we can say that one thing is before or after another thing.