His most important work, Leviathan, was published in its English edition in 1651 at the end of the English Civil War when he returned to England from France, It is generally regarded as one of the masterpieces of political theory and the greatest work of political philosophy in the English language. This book taken together with his overall corpus places him among the first of the ‘Modern Philosophers’. Before him political thought was construed as the deduction of general rules from observations of past behaviour. In contrast he believed that the study of geometry should serve as a model for the search for the principles of politics. 

Hobbes firmly rejected a fundamental premise of the commonly held opinion in political theory that a ‘body of people’ is able to live in peace and harmony. For him, as for later political writers and politicians, that belief amounted to a reification since there is no such thing as a ‘body’, just individuals.

His aphorisms that life is solitary, poor, nasty brutish and short and that in ‘a state of nature’ human beings live in constant fear and in an environment of war of all against all (bellum omnium contra omnes) continue to resonate. His fundamental and constant claim was that civil life is only possible under an absolute sovereign who has the power and authority to make life-and-death decisions on behalf of everybody. Although this prescription that individuals should covenant all their rights (except one) to an absolute sovereign (Leviathan) is unacceptable today in our European political universe, there are political elites in the twenty-first century who find no quarrel with his vision.