Empirical and conceptual objects
[edit]Objects and their properties

The world seems to contain many individual things, both physical, like apples, and abstract such as love and the number 3; the former objects are called particulars. Particulars are said to have attributes, e.g. size, shape, color, location and two particulars may have some such attributes in common. Such attributes, are also termed Universals or Properties; the nature of these, and whether they have any real existence and if so of what kind, is a long-standing issue, realism and nominalismrepresenting opposing views.

Metaphysicians concerned with questions about universals or particulars are interested in the nature of objects and their properties, and the relationship between the two. Some, e.g. Plato, argue that properties are abstract objects, existing outside of spaceand time, to which particular objects bear special relations. David Armstrong holds that universals exist in time and space but only at their instantiation and their discovery is a function of science. Others maintain that particulars are a bundle or collection of properties (specifically, a bundle of properties they have).

Biological literature contains abundant references to taxa (singular “taxon”), groups like the mammals or the poppies. Some authors claim (or at least presuppose) that taxa are real entities, that to say that an animal is included in Mammalia (the scientific name for the mammal group) is to say that it bears a certain relation to Mammalia, an abstract object.^[10] Advocates of phylogenetic nomenclature, a more nominalistic view, oppose this reading; in their opinion, calling an animal a mammal is a shorthand way of saying that it is descended from the last common ancestor of, say, humans and platypuses.^[11]

http://en.wikipedia.org/wiki/Metaphysics