Letters 102.7

Simply this: we believe that nothing is a good, if it be composed of things that are distinct. For a single good should be checked and controlled by a single soul; and the essential quality of each single good should be single. This can be proved of itself whenever you desire; in the meanwhile, however, it had to be laid aside, because our own weapons are being hurled at us.

Seneca, Letters to Lucilius 102.7, translated by Richard Mott Gummere