In Middle Ages, what the nature of intellect is was a disputed problem, so far as it was concerned with the faith on Christianity. Thomas Aquinas constructed his theories on the nature of the intellect by way of renovating the traditional philosophy on the relation between being and essence to get a metaphysical basis for his theories on the nature of the intellect. They are as follows: intellect is a power of the soul, which is the form of the body; intellect has both active power and passive power; The power of memory is the same as intellective power in part, however, reason and intellect belong to a single power with different meaning.