Hobbes thought of his theory of politics as a 'science'. At the end of his English Optical Treatise he expressed the hope that 'I shall deserve the reputation of having been ye first to lay the grounds of two sciences; this of Optiques, ye most curious, and yt other of Natural Justice, which I have done in my booke De Cive'. 1 The parallel, or distinction, between natural science and civil science recurs again and again in Hobbes's writings; and the difficulty for Hobbes's commentators lies in deciding what the relationship is between these two different types of science. Most critics have assumed that the two types are closely related, and that we therefore have to understand how Hobbes conducts his physical science in order to be able to understand his science of politics. But a few writers, most notably Tom Sorell in his important recent study of Hobbes's philosophy, have argued in favour of a so-called 'autonomy thesis', according to which Hobbes's political science is independent, qua science, of his science of nature. 2
Among interpretations which argue that Hobbes's two sciences were closely related, we can distinguish two versions of the argument: a strong version and a weak one. The strong version claims that Hobbes envisaged a single, continuous chain of derivation leading from physics, via psychology, to politics: this interpretation makes him a would-be 'social scientist' of a very literal kind, and an intellectual ancestor certainly of Comte, and possibly of Mill. The weak version, on the other hand, claims only that Hobbes applied the method of physical science to the science of politics, so that the political theory resembles or parallels the physics without necessarily being derived from it.
A classic example of the strong version of this argument can be found in Alan Ryan's book, The Philosophy of the Social Sciences:
Hobbes believed as firmly as one could that all behaviour, whether of animate or inanimate matter, was ultimately to be explained in terms of particulate motion: the laws