When you’re called upon to speak, then speak, but never about banalities like gladiators, horses, sports, food and drink – common-place stuff. Above all don’t gossip about people, praising, blaming or comparing them. Avoid fraternizing with non-philosophers. If you must, though, be careful not to sink to their level; because, you know, if a companion is dirty, his friends cannot help but get a little dirty too, no matter how clean they started out.