ABSTRACT
By what criteria are these five chapters to be judged adequate or inadequate? Plainly we are within our rights to exploit the conditions of adequacy on definitions that Hobbes himself imposes (De Corp., ch. 6, xv, E I 84). It will turn out that these conditions are not always satisfied by Hobbes's explications of universal names. Then there is the acceptability of Hobbes's Thesis to consider. Can the idea of motion have the explanatory power that Hobbes thinks it has? If not, then a first philosophy centred on the definition of motion will simply not yield the principles of the special natural sciences. It is hard to show conclusively that Hobbes's first philosophy is deficient because Hobbes's Thesis is. One would have to examine in detail the many explanations in physics he thinks can be couched in terms of locomotion (cf. e.g. SPP, DP, E VII 1-177). I shall not attempt that examination. Instead, I shall briefly return (section 4 below) to the division of the natural sciences that Hobbes's Thesis seems to inspire, and in particular to the place that geometry is supposed to occupy in that scheme. If Hobbes's Thesis is right, then geometry, like any of the special natural sciences, must be a science of motion. Hobbes can even be read as saying that it is the preeminent science of motion. His working out of this claim invites objections he never properly answers. This starts a doubt about the cogency of Hobbes's Thesis as a principle for organizing the special sciences of nature.
