Zeno would have agreed that there could be circumstances when one might choose illness for the good of the world, but for Zeno, health is a naturally preferred state; Aristo rejected this. For Aristo, not only are there times when illness might be preferred over health, (health cannot always be unconditionally preferred), but health is not even a natural advantage, and one can "never" assume that it is better than illness. Although the sage can (and often must) choose between various indifferent things, he should never make the error of assuming that they could be naturally preferred.