Keywords: Hobbes; Political Power; Knowledge; Reality.
By criticizing Aristotle's ontology, Hobbes not only intends to present a new theory of reality, but above all he pursues a practical goal, that of defending political order against the claim that (a certain idea of) truth and justice has to prevail over the imperatives of political power. In Hobbes's thought materialism is the starting point for his theory of knowledge, but it is also a tool for controlling subjects' imagination in order to preserve political consent. To this end Hobbes's theory of knowledge shifts from sensations as pressures of external bodies to the imagination of this motions and then to the connection between imaginations (or phantasms). So that political power reveals to be domination over «phantasms», and obedience is based on the correct reckoning of names (that are nothing else than phantasm of phantasms), while Leviathan appears to be indeed the Lord of phantasms.