'I thought she consented'

Should mistakes of fact be a complete defense in criminal law only when they are reasonable? Or should even unreasonable mistakes exculpate? I examine and take issue with arguments that mistakes should not have to be reasonable to be a complete defense. For the most part, however, I focus not on the general question, but on one particular defense: the defense, to a charge of rape, that "I thought s/he was consenting." Mistakes are possible regarding sexual consent, but unreasonable mistakes are possible only if the defendant was indifferent as to whether his partner consented, or at best cared too little to attend to the matter. An unreasonable mistake shows him to be culpable in roughly the same way that recklessness does, and therefore should not exculpate. This may not be true of unreasonable mistakes in general, but is true of unreasonable mistakes regarding sexual consent..