Psychology is double-ended, remarks Porfiry Petrovich in Crime and Punishment. As a method of investigation it alerts the guilty party to suspicion, and as evidence before the court it provides fodder for the defence. For instance, a murder suspect is openly interrogated about an incriminating article written before the crime: if he were planning to commit murder, he claims, he would not have published the article that has brought suspicion on himself. In The Brothers Karamazov, Fetyukovich exploits this double-endedness to refute the psychological arguments of the prosecution. Testimony regarding the behavior of the accused in crowded taverns a month before the murder may establish his malice for the victim; that he hurled threats against his father there and then also shows he was not plotting the alleged parricide at the time. Thus Fetyukovich likewise states that psychology is “a stick with two ends.”
This expression says nothing about the stick, since all sticks have two ends. It draws attention to a practice in which both ends of the stick are operative. Porfiry Petrovich and Fetyukovich are engaged in forensics when they call psychology double-ended. Yet outside such contests, in the hands of Marmeladov and Alyosha Karamazov, for example, psychology is as single-ended as mathematics. So Porfiry Petrovich conducts his investigations in casual conversation, at his home office and in public houses, while Alyosha’s psychology becomes highly dubious in court.
It is tempting to blame the double-endedness of psychology on the wiliness of its practitioners, on the mysteries of human nature or of the world as will. You can account for it by analyzing criminal reasoning and broad, “Karamazovian” natures. You would then be talking about the internal states of others – single-minded premeditations and double-sided contradictions – as if they exist independently of our techniques of determining them. And so you would be abusing psychology, or as Fetyukovich puts it, writing romance. Wittgenstein called the analogous formulation of “existential propositions” in mathematics, “the curse of prose.” For the sense of a concept is fixed only by the use we make of it. Dostoevsky’s fiction is not a laboratory, his plots are not experiments, and his characters are no more or less believable than the proposition that “two times two equals four.” He represents diverse uses of psychology to provide a conceptual background for the description of character. My paper traces the extent of Dostoevsky’s psychological skepticism and compares his achievement with mathematical proof.