This same reasoning is used to describe the essences and necessary properties of the body and mind. A thinking thing can exist with only thought as its essence and other modifications (modes) of thought such as affirmation and negation, willing and not willing. According to Descartes, the mind is conscious and not extended, while the body is extended but not conscious. Descartes uses these essences as proof that the mind and the body are two completely different things that have essentially nothing in common.