Explain Descartes' argument for the indivisibility of the mind. [5 marks]

Descartes defines the mind as something which only thinks and is not 'extended', and the body as something which is only extended but does not think. He claims that these two ideas are clearly and distinctly conceived. According to Leibniz's 'principle of the indiscernability of universals', identical substances share the same properties since it is logically contradictory to say that one substance can have different properties from itself. My mind is not divisible. The faculties of willing, perceiving, imagining and so on are in fact activities and properties of one and the same mind. Conversely, my body does have parts - I can quite literally lose a hand or a foot, for example. Therefore, since mind and body possess different properties (the body is divisible while the mind is not), they cannot be the same substance. Hence, they are two ontologically distinct substances, lending the name of 'Substance Dualism' to Descartes' theory.