Ramsey questions the distinction between subject and predicate in sentences. Since the distinction mirrors the ontological distinction object/property (particular/universal) he questions the letter distinction as well. There is a symmetry between the category of objects and the category of properties: an object can possess a number of properties and a property can be exemplified by a number of objects. Consequently, it may be claimed that the two categories are formally indiscernible. The paper develops Ramsey's thesis on the ground of logic. Different senses of indiscernibility are discussed and various systems of logic are examined with respect to these senses. Most systems do not distinguish objects from properties in at least one sense.
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