‘Civil philosophy’, Hobbes declares in an oft-quoted boast at the start of De Corpore, is a science ‘no older … than my own book De Cive’. As he later explains in Leviathan, the failure of all previous efforts has been due to their ‘want of Method’. The method followed hitherto, especially in the universities, has been to rely on the authority of selected writers and books. The universities, indeed, have come to rely so heavily on one particular writer that their teachings no longer deserve to be called philosophy, but merely Aristotelity. This approach, however, is nothing but ‘a signe of folly’, one that is ‘generally scorned with the name of Pedantry’. The only scientific way of proceeding is to follow the methods of geometry, which requires its practitioners to ‘begin at settling the significations of their words’. Only by this means can we hope to avoid the insignificant speech of the schoolmen and lay the foundations for a genuine science of political life. For ‘the foundation of all true Ratiocination, is the constant Signification of words’.

As Hobbes turns to employ this approach in Leviathan, there is no case in which he is so anxious to insist on his own definitions, and to argue that all others are dangerously misleading, as he is in explicating the concept of liberty. It is striking, moreover, that his anxieties on this score increased as he progressively refined his theory of the state.