just as we may observe that the sensibility, etc., of one is in kind different from that of another, that one responds differently from another to a given simulus, e.g. a horse behaves differently towards oats from what it does towards hay, and a dog again differently towards both, and so on. These differences can as readily be observed as that one body is harder than another, and so on.
Zentzu horretan aipatu behar da organismo bat beste bat baino sentikorragoa edo narritakorragoa edo birsorketa indar handiagokoa dela, bataren sentimena eta abar motaren arabera beste batek duenetik ezberdintzen den moduan, bata kinada jakin baten aurrean beste batek egiten duen modu ezberdinean jokatzen duen bezala, zaldiak oloaren eta lastoaren aurrean adibidez, eta zakurrak beste era batean bi horien aurrean, eta abar, eta hori gorputz bat beste bat baino gogorragoa dela eta abar behatu daitekeen bezainbat.