There is an opinion out there that there is a fine line between wisdom and nonsense. I don't agree. I believe there is a very clear line, it's just that we're not very good at seeing it.

The image, I believe, is addressing the same issue. Or again:

‘Socrates, how will you enquire into that which you do not know? What will you put forth as the subject of enquiry? And if you find what you want, how will you ever know that it is the thing which you did not know?" (Anytus - the Tanner)

I suppose the tanner has a point.