Letters 95.56

The carpenter does not need to inquire about his art in the light of its origin or of its function, any more than a pantomime need inquire about the art of dancing; if these arts understand themselves, nothing is lacking, for they do not refer to life as a whole. But virtue means the knowledge of other things besides herself: if we would learn virtue we must learn all about virtue.

Seneca, Letters to Lucilius 95.56, translated by Richard Mott Gummere