Letters 95.67

Would you, for instance, deem it a useful thing to have evidence given you by which you may recognize a thoroughbred horse, and not be cheated in your purchase or waste your time over a low-bred animal? But how much more useful it is to know the marks of a surpassingly fine soul—marks which one may appropriate from another for oneself!

Seneca, Letters to Lucilius 95.67, translated by Richard Mott Gummere