Matter, form and substance again.
Its matter is yarn, its form is the woven arrangement of the yarn. The substance is what we perceive that arrangement means to us.
A ‘sock’ exists only as far as our perception of its arrangement permits. Otherwise it is just a squiggle of yarn - the understanding of which, of course, depends on how we perceive the fibres that make up yarn, etc, etc, etc…
A sock exists in its ‘sock-ness’ as a manufactured reality in our minds. If humans had never existed and somehow the matter of a ‘sock’ came to exist in a ‘sock-like’ form it would never be perceived as a human sock and therefore it would not BE a sock since there would be noone to manufacture that reality.
That is nominalism, or at the very best conceptualism. Most Catholic philosophers are either Realist or moderate Realists., such as Aquinas, Scotus and Mayrone. The Nominalists such as Ockham have been refuted on these points by systematic application of logic. I will give an example from Scotus Ordinatio II. D3, part 1, QQ3 : 59-64
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Because what is not of itself distinct or determinate cannot be what first distinguishes or determines something else. But the being of existence, in the sense in which it is distinguished from the being of essence, is not itself distinct or determinate. For the being of existence does not have its own differences other than the differences of the being of essence, because in that case one would have to posit a proper heirardchy of existences other than the heirarchy of essences. rather the being of existence is precisely determined from something else’s determination. Therefore, it does not determine anything else;
From this, one could argue another way; what presupposes the determination and distinction of another is not th ereason for distungishing or determining that other. But existence, as determined and distinct, presupposes te heirarchy and distinction of essences. Therefore etc.
If it is said that it presupposes every other distinction than the distinction into individuals, but it causes the distinction that so to speak results in the individual, then to the contrary; in a categorical heirarchy, there are contained all the things that pertain by themselves to that heirarchy, disregarding whatever is irrelevant to the hierarchy. According to Aristotle (Posterior Analytics I; 20,82a21-24) “there is an end-point in each category, at the high end and at the low end” therefore, just as there is found a highest in a genus, considering it precisely under the aspect of essence, so there are found intermediate genera, and species and differences. There is also found there a lowest, namely, the silgular – actual existence, being disregarded altogether. This is plainly evident because “this man” does not formally include actual existence any more than “man” in general does.
Furthermore there is the same question about existence as there is about nature; by what and from where is it contracted, so that it is “this” if the specific nature is the same in several individuals, it has the same king of existence in them. Just as it is proved in the solution to the first Question; that the nature is not of itself a “this” so too it can be asked what it is through which existence is a “this” because it is not “this” of itself. So it is not enough to give existence as that by which the nature is a “this”.””
Clearly from this it follows that that within a genus is individuated by that which is within it; or that which is intrinsic to it; for although an act distinguishes; only an essential act distinguishes essentially - and an accidental act (as that of a nominalism) does only distinguish accidentally; and thus although generative has no meaningful distinction; wheras that which distinguishes as to the material substance of an object distinguishes as to what it is inhered; and not to that which is accidentally predicated thereof.
The act of a sock in praxis is only an accidental act; and cannot distinguish essentially; thus that distinction as to what individuates a sock is that which is inhered; and not that which is predicated in accidents; such as an accidental praxis.