 Finally, Plutarch wrote a number of works on aspects and figures of the history of philosophy, all lost, such as On What Heraclitus Maintained (#205), On Empedocles (#43), On the Cyrenaics (#188), On the Difference between Pyrrhonians and Academics (#64), On the Unity of the Academy Since Plato (#63). The latter two could not have been merely historical, however; the historical perspective must rather have served to defend the point of view of the skeptical Academy, which Plutarch advocated as doing justice to the aporetic spirit of Plato's philosophy (see below, sect. 2).