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On Hume’s ‘Of abstract ideas’ (from The Treatise)

I had to reread Hume’s ‘Of abstract ideas’ a few times to get it, but I think I understand it now. First he says that it is absurd to think that we have an idea that represents all different shapes and sizes of, for example, ‘man’, because that would seem to require and infinite capacity in the mind. He then goes on to argue why it can’t also be the opposite: that our general ideas represent no particular degree of quantity and quality, and thus I suppose are just kind of blueprints with the appropriate ratio among these quantities/qualities.

Firstly, he talks about how you can’t separate the the particular degree from the quality/quantity you are dealing with. Hume says, “But ’tis evident at first sight, that the precise length of a line is not different nor distinguishable from the line itself; nor the precise degree of any quality from the quality.” So he basically just asserts that it is evident.

Secondly, he argues that since all experience is particular, all of our impressions are of particular things with particular degrees of quality/quantity. And according to his own definition of the principle by which our ideas come to be, “all ideas…are nothing but copies and representations of them (impressions), whatever is true of the one must be acknowledg’d concerning the other…An idea is a weaker impression; and as a strong impression must necessarily have a determinate quantity and quality, the case must be the same with its copy or representative.”

Thirdly, Hume seems to be making a very similar point to the second. Everything in nature is individual, therefore everything has a particular degree of all of its qualities/quantities. This is therefore absurd in ideas to have an object without degree (his second point), “since nothing of which we can form a clear and distinct idea is absurd and impossible.” I guess by the latter he means that since our ideas are of particular degree (of a once perceived impression of this degree), that whatever cobbled together idea of the imagination we come up with must not be impossible since it is composed of ideas of parcular degree. There is one sentence in this paragraph that I can’t quite decipher, “But to form the idea of an object, and to form an idea simply is the same thing; the reference of the idea to an object being an extraneous denomination, of which in itself it bears no mark or character.” After that he just goes on to say that just as it is absurd to say we have ideas that have quality but no precise degree, it is likewise equally absurd to say that the ideas have quality/quantity “that is not limited and confin’d.”

Hume’s first point seems arcane, and I’m not sure what the reasoning is behind this argument that degree and quality can’t be separated. The second depends on his own definition of terms, which seems to be a very weak reason. The third follows the second with his idea of this copying of impressions into ideas, and just extends the second argument to the case of unlimited degrees. Anyways, Hume’s point is that our images in the mind are only of particular objects, and that these are applied an universals/abstract ideas.

It seems to me that in order to find a resemblance among particulars, to the extent that I am able to form some general/abstract idea and identify further particulars of as to yet unencountered degree, would have to point to a faculty that isn’t recognizing particular degree, and is instead recognizing the form. Hume seems concerned with the particular idea, the idea that comes to mind, that when someone says ‘triangle’, the idea that I have is my abstract idea of ‘triangle’, and according to his own principles, it must be of an encountered particular.