Letter 121 — On Instinct in Animals (§17)

“First of all, the living being is adapted to itself, for there must be a pattern to which all other things may be referred. I seek pleasure; for whom? For myself. I am therefore looking out for myself. I shrink from pain; on behalf of whom? Myself. Therefore, I am looking out for myself. Since I gauge all my actions with reference to my own welfare, I am looking out for myself before all else. This quality exists in all living beings—not engrafted but inborn.”