Akrasia

The problem of ἀκρασία * shows:

1) Knowledge is not the sole basis for action.
2) Since action is the most vital criteria for determining the possession of knowledge, the akratic man only thinks he knows, but does not in actual fact.
OR
3) Our conception of knowledge and it's relation to action is problematic.

* Lack of control over one's own actions. In particular, I am talking about when someone claims to know that doing A is best, but does B anyway.