Arcesilaus maintained that nothing at all could be grasped by the mind, but in so affirming affirmed that that nothing at all could be grasped by the mind could be grasped by the mind. Carneades, however, recognized that it was entirely self-contradictory to affirm that nothing is affirmable, or to affirm that it can be grasped that nothing is graspable. Scholars therefore argue that Carneades is the less radical skeptic because in failing to affirm that nothing can be grasped he seems to leave open the possibility that something can be grasped (even if this could never be affirmed).
I want to argue that Carneades is a weaker skeptic for another reason: namely that in his very refusal to affirm that nothing is affirmable for the sake of consistency, he is implicitly adopting a criterion for truth: the law of non-contradiction. Arcesilaus is more radical because he recognizes that even the principle of non-contradiction cannot be an irrefutable criterion of truth, since the skeptic maintains that no such criterion for truth exists. Carneades is less radical only because he is, insofar as he is attempting to be consistent, inconsistent with his skepticism, since consistency cannot be a criterion for truth according to skepticism. It seems that consistency cannot even be a value for the radical skeptic.