  The essence of mind is thought. Besides existence and duration, minds have  the two chief powers or faculties previously mentioned: intellect and will. The intellectual (or perceiving) power is further divided into the modes of pure intellect, imagination, and sense perception. Pure intellect operates independently of the brain or body; imagination and sense perception depend upon the body for their operation (as does corporeal memory). The will is also divided into various modes, including desire, aversion, assertion, denial, and doubt. These always require some intellectual content (whether pure, imagined, or sensory) upon which to operate. Perhaps for that reason, Descartes describes the mind as an “intellectual substance” (7:78; also, 7:12). It seems he held that  the mind essentially has a will, but that the intellectual (or perceptive, or representational) power is more basic, because the will depends on it in its operation.