How valid are these criticisms?
Plato's theory of forms outlines his metaphysical, dualistic vision of reality. Plato's dualism consists of two realms: the visible realm and the intelligible realm. These two worlds sit in stark contrast to each other. However, his theory has encountered much criticism since its innovation. Criticisms originate from Aristotle (384-322 BCE), Bertrand Russell (1872-1970) and even Plato (429-347 BCE) himself.
Aristotle is arguably the most critical of Plato' theory for within his work: Metaphysics. It is clear that his Third Man argument is his strongest argument. This argument can be considered valid as it poses the question of what things make up the essence of a form, therefore how can there a perfect form of bigness when so many objects incorporate bigness. Moreover, this theory is valid as it's repeatable for example according to Aristotle's argument there cannot be a perfect form of light, due to the light essence varying; the sun, torch, fire.
This argument unravels Plato's theory as there is no counter-argument or information within his theory and is repeatable and therefore is a valid argument.
On the other hand, this argument can be seen as invalid because Plato never specifies the essences that make up a form, therefore you can't just presume as Aristotle does and take a characteristic of a form such as how big it is and then use that as a justification to conclude that there is no perfect form of big as other objects incorporate varying levels of bigness.
Bertrand Russell criticised Plato's theory by highlighting the gap between universals and particulars. For example, I can say 'Socrates is human,' 'Plato is human,' and so on. In all these statements, it may be assumed that the word 'human' has exactly the same meaning. But whatever it means,