Like Socrates the benefit of saying you do not know gives one the motivation of finding out.

Moreover, as Socrates told his interlocutors, his acknowledgment that he did not know had the salutary effect of making it possible for him to find out. If he were sure that he already knew, then he would not have motivation to look for the answer.

It was possible for Socrates to be both sure he did not know what virtue was and yet confident that it was something beneficial to the soul

Then one has the problem what is 'soul' and what is 'virtue'?

 Cleansing your mental house of beliefs
In contrast, Descartes in his Meditations set out to rid himself of all beliefs in order to rebuild his edifice of belief from scratch, so as to avoid all possibility of erroneous foundations. C