Campbell, like most theorists of the Enlightenment, believed in a universal human nature: the "general principles taste are the same in every people". He gives the example of tropes and figuration which "are so far from being the inventions of art, that, on the contrary, they result from the original and essential principles of the human mind". This facet of human nature has remained constant throughout history so it must be universal trait. Based on premises similar to this, Campbell claimed that human beings act according to clear and obvious motives and rhetoric should be, in turn, directed towards similar operations of the mind.