I was reading a Dorothy Sayers essay about Dante the other day in which she discussed the manner in which the souls in Inferno have become identified with their sin. She was quite emphatic in pointing out the fundamental distinction between Dante's and the readers' journey through hell and the status of the sinners within hell. Those who remain in hell have chosen sin through a deliberate action of the will: an action which could not be more dissimilar from that of Dante and the readers who only witness the punishments to see what accepting the temptations of sin will lead to.
This point rather leads her off onto a tangent. She tells of a letter she once received from a student with very definite ideas about psychology (a young man of that type so thoroughly convinced of his own modernity in accepting certain ideas that he'll hold onto them far past the threshold of illogicality). He tried, she writes, to persuade her that her writing of mystery stories revealed a suppressed impulse to actually commit a murder, basing his idea on the assumption that the unconscious is the sum of the mind and ignoring the function of rational choice in defining a person's state.
Sayers relates this odd correspondence to her belief that it is invalid to identify impulse and the human unconscious too exclusively with the activity of the mind. Ultimately, the tendency to say that the unconcious is all that genuinely exists in the mind leads one to reject both intellect and will (two fundamental concepts for Dante) - the rational and directive capacities of the mind. To reject these two is to reject precsely that aspect of the mind which makes us human (a very convenient rejection if you want to define man as no more than a particularly clever ape). If, as the student she writes of says, the impulse to write a murder story and the impulse to murder are one and the same, we would have to admit that simple thinking about something is morally equivalent to doing it.
But wait... perhaps you're not supposed to talk about morals nowadays... Nonetheless, even if you were to discount all language of morality, you must admit that such an idea promotes something of a logical fallacy: it identifies an impulse that is actualized as being identical to an impulse that is merely felt; it refuses to consider action and views consideration as all that counts. No assent of will can distinguish the actor from the mere contemplator. The view discounts the decision to either act on or reject an impulse and holds that only the impulse itself is of any account.
In more Dantean language, it denies sin by making temptation itself into the only thing that counts in the human mind. Sin is inflicted on people by circumstances which cause temptation to arise, rather than being - as Dante believed - a concious choise of the individual's will to act according to temptation and against what the intellect informs it is right.