This term was used by T.S. Eliot in the essay "Hamlet and His Problems": "The only way of expressing emotion in the form of art is by finding an objective correlative; in other words, a set of objects, a situation, a chain of events which shall be the formula of that particular emotion; such that when the external facts, which must terminate in sensory experience, are given, the emotion is immediately evoked." This definition relates to the impersonal theory of poetry that Eliot held in such high regard. According to this theory, if poetry is simply an expression of personal emotion, it carries no significance beyond that person and so offers nothing new to extend tradition or meaning to the world. The formula for an emotion, on the other hand, can have meaning for almost anyone who is willing to pay close attention to the objects or events in that formula.
Here is the excerpt from the essay:
"The only way of expressing emotion in the form of art is by finding an “objective correlative”; in other words, a set of objects, a situation, a chain of events which shall be the formula of that particular emotion; such that when the external facts, which must terminate in sensory experience, are given, the emotion is immediately evoked. If you examine any of Shakespeare’s more successful tragedies, you will find this exact equivalence; you will find that the state of mind of Lady Macbeth walking in her sleep has been communicated to you by a skilful accumulation of imagined sensory impressions; the words of Macbeth on hearing of his wife’s death strike us as if, given the sequence of events, these words were automatically released by the last event in the series. The artistic “inevitability” lies in this complete adequacy of the external to the emotion; and this is precisely what is deficient in Hamlet. Hamlet (the man) is dominated by an emotion which is inexpressible, because it is in excess of the facts as they appear. And the supposed identity of Hamlet with his author is genuine to this point: that Hamlet’s bafflement at the absence of objective equivalent to his feelings is a prolongation of the bafflement of his creator in the face of his artistic problem. Hamlet is up against the difficulty that his disgust is occasioned by his mother, but that his mother is not an adequate equivalent for it; his disgust envelops and exceeds her. It is thus a feeling which he cannot understand; he cannot objectify it, and it therefore remains to poison life and obstruct action. None of the possible actions can satisfy it; and nothing that Shakespeare can do with the plot can express Hamlet for him. And it must be noticed that the very nature of the données of the problem precludes objective equivalence. To have heightened the criminality of Gertrude would have been to provide the formula for a totally different emotion in Hamlet; it is just because her character is so negative and insignificant that she arouses in Hamlet the feeling which she is incapable of representing."
