Letters 95.44

I think, then, that there should be deeply implanted a firm belief which will apply to life as a whole: this is what I call a “doctrine.” And as this belief is, so will be our acts and our thoughts. As our acts and our thoughts are, so will our lives be. It is not enough, when a man is arranging his existence as a whole, to give him advice about details.

Seneca, Letters to Lucilius 95.44, translated by Richard Mott Gummere