Reason is computation or reckoning for Hobbes.
There are two major discussions of reason, of which the later one in De Corpore is simpler and more moderate than the earlier one in Leviathan . Theoretically the discussion of reason is also more crucial to De Corpore since it is the first section of Hobbes's complete system of scientific knowledge, The Elements of Philosophy . Hobbes thinks that if the foundations of a science are uncertain, then so are all of its results. In both Leviathan and De Corpore reasoning is said to be addition and subtraction. Hobbes illustrates the idea from arithmetic, geometry, and language.