I’m surprised that, after studying free will for several years, I’ve never heard philosophers mention the story of The Scorpion and The Frog.
The story is simple. A scorpion asks a frog to carry him across the river. The frog is afraid of being stung. But the scorpion reassures the frog that, if stung, the frog would drown, and therefore so would the scorpion. The frog agrees. Halfway through, the scorpion stings the frog. They will both drown. The frog asks the scorpion, “why?” The scorpion says, “I’m a scorpion; it’s my nature.”
The Scorpion and the Frog illustrate a fundamental distinction: between defects in a person’s rationality (r-defects) and defects in a person’s desires and values (v-defects). The scorpion has a v-defect, but not necessarily an r-defect. The v-defect is clear: he wants to sting, and stings, innocents. Is it the scorpion’s fault that he has the character he does? No. And then, in accordance with TNR-like principles, isn’t the scorpion excused?
To my eyes, the story of the Scorpion and the Frog exposes a blind spot in compatibilism. Quite simply: compatibilists seem to never consider v-defects to be excusing conditions. All of the standard accounts (Fischer’s, Dennett’s, etc.) seem blind to v-defects. Fischer considers whether a person is reasons-responsive—regardless of what the reasons are. Frankfurt considers whether a person acts in accordance with his highest desire—regardless of what that desire is. Well, what if, through no fault of his own, that person’s highest desire is to torture and murder other people?
The scorpion does not necessarily have an r-defect. Indeed, the scorpion can satisfy the compatibilist conditions of your choice. He can be reasons-responsive and own his reasons-responsive mechanism. He might act in accordance with his highest desire—to sting others (even if he drowns). He might, in other words, be perfectly rational.
For example, the scorpion doesn’t say “well, it’s my character to be friendly and peaceful, but then this random, inexplicable urge to sting you gripped me.” That r-defect would excuse the scorpion even in the eyes of compatibilists. But he doesn’t say that. He says, “I’m a scorpion; it’s my nature.” Yet he still seems excused.
Instead of just considering defects that could impair a person’s rationality, we should also consider defects in a person’s desires and values. They can be just as hurtful. And they should be just as exculpating.