Platonism, rendered as a proper noun, is the philosophy of Plato or the name of other philosophical systems considered closely derived from it. In narrower usage, platonism, rendered as a common noun (with a lower case 'p', subject to sentence case), refers to the philosophy that affirms the existence of abstract objects, which are asserted to "exist" in a "third realm" distinct both from the sensible external world and from the internal world of consciousness, and is the opposite of nominalism (with a lower case "n"). Lower case "platonists" need not accept any of the doctrines of Plato.