Epictetus, Golden Sayings 175

Never call yourself a Philosopher, nor talk much among the unlearned about Principles, but do that which follows from them. 

Thus at a banquet, do not discuss how people ought to eat; but eat as you ought. 

Remember that Socrates thus entirely avoided ostentation. Men would come to him desiring to be recommended to philosophers, and he would conduct them thither himself—so well did he bear being overlooked. 

Accordingly, if any talk concerning principles should arise among the unlearned, be you for the most part silent. For you run great risk of spewing up what you have ill digested. 

And when a man tells you that you know nothing, and you are not nettled at it, then you may be sure that you have begun the work. 

IMAGE: Pier Francesco Mola, The Teachings of Socrates (c. 1660)