P56: There are as many species of Joy, Sadness, and Desire, and consequently of each affect composed of these (like vacillation of mind) or derived from them (like Love, Hate, Hope, Fear, etc.), as there are species of objects by which we are affected.

Dem.: Joy and Sadness—and consequently the affects composed of them or derived from them—are passions (by P11 S). But we are necessarily acted on (by P1) insofar as we have inadequate ideas, and only insofar as we have them (by P3) are we acted on, i.e. (see IIP40 S), necessarily we are acted on only insofar as we imagine, or (see IIP17 and P17 S) insofar as we are affected with an affect that involves both the nature of our Body and the nature of an external body. Therefore, the nature of each passion must necessarily be so explained that the nature of the object by which we are affected is expressed.

For example, the Joy arising from A involves the nature of object A, that arising from object B involves the nature of object B, and so these two affects of Joy are by nature different, because they arise from causes of a different nature. So also the affect of Sadness arising from one object is different in nature from the Sadness stemming from another cause. The same must also be understood of Love, Hate, Hope, Fear, Vacillation of mind, etc.

Therefore, there are as many species of Joy, Sadness, Love, Hate, etc., as there are species of objects by which we are affected.

But Desire is the very essence, or nature, of each {man} insofar as it is conceived to be determined, by whatever constitution he has, to do something (see P9 S). Therefore, as each {man} is affected by external causes with this or that species of Joy, Sadness, Love, Hate, etc. —i.e., as his nature is constituted in one way or the other, so his Desires vary and the nature of one Desire must differ from the nature of the other as much as the affects from which each arises differ from one another.

Therefore, there are as many species of Desire as there are species of Joy, Sadness, Love, etc., and consequently (through what has already been shown) as there are species of objects by which we are affected, q.e.d.

Schol.: Noteworthy among these species of affects—which (by P56) must be very many—are Gluttony, Drunkenness, Lust, Greed, and Ambition, which are only notions of Love or Desire which explain the nature of each of these affects through the objects to which they are related. For by Gluttony, Drunkenness, Lust, Greed, and Ambition we understand nothing but an immoderate Love or Desire for eating, drinking, sexual union, wealth, and esteem.

Moreover, these affects, insofar as we distinguish them from the others only through the object to which they are related, do not have opposites. For Moderation, which we usually oppose to Gluttony, Sobriety which we usually oppose to Drunkenness, and Chastity, which we usually oppose to Lust, are not affects or passions, but indicate the power of the mind, a power that moderates these affects.

I cannot explain the other species of affects here—for there are as many as there are species of objects. But even if I could, it is not necessary. For our purpose, which is to determine the powers of the {II/186} affects and the power of the Mind over the affects, it is enough to have a general definition of each affect. It is enough, I say, for us to understand the common properties of the affects and of the Mind, so that we can determine what sort of power, and how great a power, the Mind has to moderate and restrain the affects. So though there is a great difference between this or that affect of Love, Hate or Desire—e.g., between the Love of one’s children and the Love of one’s wife—it is still not necessary for us to know these differences, nor to investigate the nature and origin of the affects further.