Know Thyself, Dude

Like the man said 
Before he drank his last 
Bitter draught toasting 
Man’s stupidity, 
One thing only I know, 
And that is that 
I know nothing. 
. 

Say you do not know, 
You know. 
. 

Say you know, 
You do not know. 
. 

You know? 
. 

If not, you must be 
Some kind of stupid.