In his book The Educated Imagination, the great literary theorist Northrop Frye wrote that the poet employs
two crude, primitive, archaic forms of thought (simile and metaphor) in the most uninhibited way, because his job is not to describe nature, but to show you a world completely absorbed and possessed by the human mind.
In this passage, Frye defends and even celebrates the use of simile and metaphor, although in the passage immediately preceding this one he had wisely cautioned that any declaring of similarities must be done with caution if one wants to be purely rational and logical. Indeed, he argues in that earlier passage that metaphor, almost by definition, is irrational and illogical because it declares that two different things are the same thing – a logical contradiction, pure and simple.
In the passage quoted above, however, Frye argues that in poetry (by which he means literature in general), simile and metaphor are important and crucial instruments of writing. The poet’s purpose, he says, is not simply to describe what really exists but is instead to show how reality and existence are understood and depicted by the human mind. We do not go to literature for completely accurate descriptions of reality (we go to science for that). Instead, we go to literature to see all the various ways in which human beings are capable of thinking and feeling about reality. Literature, then, is a presentation not of reality per se but of human responses to reality, including the ways humans have tried to make sense of reality by seeing likeness between different things. Similes and metaphors are important instruments that imaginative writers use to express their feelings about reality and their perceptions of it.