I am not a philosopher by any means, so maybe I am using some words incorrectly — i.e. I am not sure what the difference is between "conceptual" and "abstract". Please correct me if I am wrong.

I've been trying to prove a point that we think in abstractions — for example, when we think about a physical object, we abstract away a lot of its physical details. This goes even further when we deal with several objects of the same category — when I count pebbles, my brain needs to first put each pebble into the object category of "pebbles" before it becomes countable (enumerable?).

The question is, are object categories themselves abstract? Abstract is defined as existing in thought or as an idea but not having a physical or concrete existence. On one hand, real pebbles exist. On the other hand, "pebbles" as a category, does not have a physical existence.

  • 2
    See Abstract objects and see Universal (metaphysics) "Paradigmatically, universals are abstract (e.g. humanity), whereas particulars are concrete (e.g. the personhood of Socrates). However, universals are not necessarily abstract and particulars are not necessarily concrete. For example, one might hold that numbers are particular yet abstract objects. Likewise, some philosophers, such as D.M. Armstrong, consider universals to be concrete." Apr 10, 2018 at 6:16
  • @MauroALLEGRANZA Thanks! So there is no consensus on this issue? Apr 10, 2018 at 6:28

1 Answer 1


I think that there is no clearly superior answer, as to whether e.g. the pebble category is abstract. Both answers, yes or no, have some plausible support.

On the one hand, one may hold that only particular entities (e.g. particular pebbles) exist, and the category is merely a more or less rough similarity that we abstract from the particulars. Hence, that the category is abstract.

On the other hand, one may hold that there is something common to particular pebbles, the essence of pebbles, which we may call e.g. ‘pebblehood’. And that pebblehood is in particular pebbles, a constitutive part of pebbles. We talk similarly about the humanity inside particular human beings. And in this case, the category denotes the essence, something that actually exists inside every particular of a given kind. And to this extent it is concrete, not abstract.

  • Should the definitions be restricted by experience? I mean we can define "flying unicorns" or "cars" and use such definitions to imagine other worlds with that objects. So does the category of cars contains all the possible cars or only the cars of our world?
    – ado sar
    Jul 30, 2020 at 23:37
  • @adosar Why would we put such limits? Yes I think that the category of cars contains all possible cars. That's why we call them possible cars, rather than e.g. possible tables. Jul 31, 2020 at 21:40

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