What is the difference between the criminal conspiracy and the aiding and abetting theories?

The chief difference in the theories is that conspiracy requires an agreement to commit a crime, while aiding and abetting requires only that the accomplice intend to facilitate another's contemplated crime. (People v. Luparello (1986) 187 Cal.App.3d 410, 439, 231 Cal.Rptr. 832.) Under both theories, however, the extension of liability to additional, reasonably foreseeable offenses rests on the policy that accomplices "should be responsible for the criminal harms they have naturally, probably and foreseeably put in motion." (Ibid.) In either case, the justice of holding the accomplice responsible for acts of the perpetrator, acts unintended by the accomplice, derives from the criminal intent of the accomplice himself and the foreseeability that the perpetrator might go beyond the accomplice's original criminal goals. For this reason, we reject defendant's argument that the natural and probable consequences rule should have a broader reach when it is couched in conspiracy terms than when it is presented as part of the aiding and abetting theory. ⁹