Epictetus

The importance of the beard to Roman philosophers is best seen by the extreme value that the Stoic philosopher Epictetus placed on it. 

As historian John Sellars puts it, Epictetus "affirmed the philosopher's beard as something almost sacred...to express the idea that philosophy is no mere intellectual hobby but rather a way of life that, by definition, transforms every aspect of one's behavior, including one's shaving habits. 

If someone continues to shave in order to look the part of a respectable Roman citizen, it is clear that they have not yet embraced philosophy conceived as a way of life and have not yet escaped the social customs of the majority...the true philosopher will only act according to reason or according to nature, rejecting the arbitrary conventions that guide the behavior of everyone else."