Letter 121 — On Instinct in Animals (§21)

“If, however, you require an explanation, shall I tell you how it is that every living thing tries to understand that which is harmful? It feels that it is constructed of flesh; and so it perceives to what an extent flesh may be cut or burned or crushed, and what animals are equipped with the power of doing this damage; it is of animals of this sort that it derives an unfavourable and hostile idea.”