"I know one thing; that I know nothing"
Do you want to explain it? It's a contradiction on it's own terms. And it's not true that one knows nothing. I don't like convoluted "clever" rhetoric because it can provide false interpretations that confuse people and gives them a misunderstanding about how things operate.
Hah, you ask a good question, I knew I should have prepared before commenting !! It's not so easy to explain what he means by this without going deeper into Plato/Socrates. Socrates was known for his inquisitive style of teaching philosophy. Oftentimes it would start with somebody making a claim, and Socrates asking questions which slowly uncover the errors in thinking of the one who said it. Socrates often 'acted the fool' and was thus the wiser man.
I found this excellent summary of Socrates' 'lack of knowledge' online which I will copy/paste here:
[quote]
"You need the full quote/ story to begin to understand this quote. Plato gives a version of the story from the mouth of his Socrates, in his ‘Apology for Socrates’.
Socrates had a friend named Chaerephon who went to the Oracle at Delphi and asked if any man was wiser than Socrates. The Oracle replied that no-one was wiser than Socrates.
Socrate heard about this and was confused and troubled by the answer. Socrates says that he is very conscious of the fact that he is not wise at all. Yet he knows the Oracle to be the voice of the Gods and spoke the truth, he must therefore be the wisest. This seemed paradoxical to him.
So Socrates went out and sought wise men and he questioned them. When he challenged their wisdom through questions, the wise would become angry and avoid him.
Socrates decides that he is in fact wiser than these men. For the ‘wise’ believe that they are wise and many around them believe in their wisdom. Socrates finds that neither of them knows anything worthwhile but the wise believe they know something and yet they do not anything worthwhile. Socrates at least realises that he does not know anything worthwhile. Socrates paraphrases the Oracle to have meant ‘human wisdom is worthless, the wisest are those who like Socrates know that their wisdom is worthless’.
The story is subversive (which is ironic as Socrates tells this story in his defence when accused of subversion). The first people that he said that he challenged were the politicians who led Athens. Socrates asserts the right of the philosopher to challenge authority and the right of the fool to be a philosopher.
For Socrates perhaps, wisdom is to be found in questions and not in answers.
[/endquote]
I think that does a decent job at explaining.