Apply the assertions of a Substance Dualist on the question of the existence of a soul.

Substance dualists would assert that there is indeed a soul. Substance dualism is the belief that there are two distinct ontological substances which causally interact, the immaterial mind and material body. There are two key historical proponents of "hard" substance dualism, Plato and Descartes. Plato would disagree with the statement, and he argued that the soul is an immutable and immaterial substance imprisoned in the body. It contains innate apriori knowledge, as it pre-existed in the noumenal realm, and is the essence of human nature, the efficient cause of movement in the body. Plato also claimed that when we learn concepts we are simply recollecting, from out soul, our past lives in the world of Forms, where we were able to acquire knowledge of them. This concept of recollection is called 'Anamnesis'. An indirect argument for the soul arises from Plato's view that knowledge of necessary truths and "perfect" universals (mathematical, geometric and ethical concepts) cannot be drawn from fluxive empirical data; hence knowledge of such things (particulars of universal forms) is innate and recollected (anamnesis). Either way, Plato strongly agrees with this statement.