 The killjoy theory categorizes metaphors as "dead", that is it asserts that modern day speakers are not aware of the comparison made between source and target domains in the everyday metaphors they use.For example, many are not cognizant that the phrase "to come to a head" refers to the accumulation of pus in a pimple.In contrast, the messianic theory correlates more closely with Lakoff and Johnson's idea of a conceptual metaphor.