 In De Corpore Hobbes first describes the view that reasoning is computation early in chapter one. “By reasoning”, he says “I understand computation. And to compute is to collect the sum of many things added together at the same time, or to know the remainder when one thing has been taken from another. To reason therefore is the same as to add or to subtract” (Hobbes 1655, 1.2). In the section that follows, Hobbes gives some initial examples of addition in reasoning, which are examples of adding ideas together to form more complex ones. Thus “from the conceptions of a quadrilateral figure, an equilateral figure, and a rectangular figure the conception of a square is composed” (Hobbes 1655, 1.3). That’s but a small part of our mental activity though. Hobbes also describes propositions and syllogisms as sorts of addition: