Intellectus. This word in St Thomas means sometimes the faculty of 'understanding'; sometimes, as here, the act, or habit of understanding, of which so much is made in modern philosophy under the name of 'intuition.' St Thomas too makes much of it. Thus his intellectus principiorum is 'intuition of first principles.' The corresponding Aristotelian and Platonic word is nous as distinguished from dianoia. Kant's 'Reason' is his equivalent for nous and intellectus.