Third man argument

The third man argument (commonly referred to as TMA; Greek: τρίτος ἄνθρωπος), first offered by Plato in his dialogue Parmenides (132a–b), is a philosophical criticism of Plato's own theory of Forms. This argument was furthered by Aristotle (Metaphysics 990b17=1079a13, 1039a2; Sophistic Refutations 178b36 ff.) who used the example of a man (hence the name of the argument) to explain this objection to Plato's theory; he posits that if a man is a man because he partakes in the form of man, then a third form would be required to explain how man and the form of man are both man, and so on, ad infinitum.