P33: Men can disagree in nature insofar as they are torn by affects which are passions; and to that extent also one and the same man is changeable and inconstant.

Dem.: The nature, or essence, of the affects cannot be explained through our essence, or nature, alone (by IIID1 and D2), but must be defined by the power, i.e. (by IIIP7), by the nature of external causes compared with our own. That is why there are as many species of each affect as there are species of objects by which we are affected (see IIIP56); that is why men are affected differently by one and the same object (see IIIP51), and to that extent, disagree in nature. And finally, that is also why one and the same man (again, by IIIP51) is affected differently toward the same object, and to that extent is changeable, etc., q.e.d.