So also the lusts and appetites of insects, fishes, and birds must needs very according to the several natures. Thus, although each individual lives content and rejoices in that nature belonging to him wherein he has his being, yet the life, wherein each is content and rejoices, is nothing else but the idea, or soul, of the said individual, and hence the joy of one only differs in nature from the joy of another, to the extent that the essence of one differs from the essence of another. Lastly, it follows from the foregoing proposition, that there is no small difference between the joy which actuates, say, a drunkard, and the joy possessed by a philosopher, as I just mention here by the way. Thus far I have treated of the emotions attributable to man, in so far as he is passive. It remains to add a few words on those attributable to him in so far as he is active.
LVIII. Besides pleasure and desire, which are passivities or passions, there are other emotions derived from pleasure and desire, which are attributable to us in so far as we are active.
Proof--When the mind conceives itself and its power of activity, it feels pleasure (III. liii.): now the mind necessarily contemplates itself, when it conceives a true or adequate idea (II. xliii). But the mind does conceive certain adequate ideas (II. xl. note ii.). Therefore it feels pleasure in so far as it is active (III. i.). Again, the mind, both in so far as it has clear and distinct ideas, and in so far as it has confused ideas, endeavours to persist in its own being (III. ix.); but by such an endeavour we mean desire (by the note to the same Prop.); therefore, desire is also attributable to us, in so far as we understand, or (III. i.) in so far as we are active. Q.E.D.
LIX. Among all the emotions attributable to the mind as active, there are none which cannot be referred to pleasure or desire.
Proof--All emotions can be referred to desire, pleasure, or pain, as their definitions, already given, show. Now by pain we mean that the mind's power of thinking is diminished or checked (III. xi. and note); therefore, in so far as the mind feels pain, its power of understanding, that is, of activity, is diminished or checked (III. i.); therefore, no painful emotions can be attributed to the mind in virtue of its being active, but only emotions of pleasure and desire, which (by the last Prop.) are attributable to the mind in that condition. Q.E.D.
*****Note--All actions following from emotion, which are attributable to the mind in virtue of its understanding, I set down to "strength of character" ("fortitudo"), which I divide into "courage" ("animositas") and "highmindedness"
("generositas"). By "courage" I mean "the desire whereby every man strives to preserve his own being in accordance solely with the dictates of reason." By "highmindedness" I mean "the desire whereby every man endeavours, solely under the dictates of reason, to aid other men and to unite them to himself in friendship." Those actions, therefore, which have regard solely to the good of the agent I set down to courage, those which aim at the good of others I set down to highmindedness. Thus temperance, sobriety, and presence of mind in danger, &c., are varieties of courage; courtesy, mercy, &c., are varieties of highmindedness.
I think I have thus explained, and displayed through their primary causes the principal emotions and vacillations of spirit, which arise from the combination of the three primary emotions, to wit, desire, pleasure, and pain. It is evident from what I have said, that we are in many ways driven about by external causes, and that like waves of the sea driven by contrary winds we toss to and fro unwitting of the issue and of our fate. But I have said, that I have only set forth the chief conflicting emotions, not all that might be given. For, by proceeding in the same way as above, we can easily show that love is united to repentance, scorn, shame, &c. I think everyone will agree from what has been said, that the emotions may be compounded one with another in so many ways, and so many variations may arise therefrom, as to exceed all possibility of computation. However, for my purpose, it is enough to have enumerated the most important; to reckon up the rest which I have omitted would be more curious than profitable. It remains to remark concerning love, that it very often happens that while we are enjoying a thing which we longed for, the body, from the act of enjoyment, acquires a new disposition, whereby it is determined in another way, other images of things are aroused in it, and the mind begins to conceive and desire something fresh. For example, when we conceive something which generally delights us with its flavour, we desire to enjoy, that is, to eat it. But whilst we are thus enjoying it, the stomach is filled and the body is otherwise disposed. If, therefore, when the body is thus otherwise disposed, the image of the food which is present be stimulated, and consequently the endeavour or desire to eat it be stimulated also, the new disposition of the body will feel repugnance to the desire or attempt, and consequently the presence of the food which we formerly longed for will become odious. This revulsion of feeling is called "satiety" or weariness. For the rest, I have neglected the outward modifications of the body observable in emotions, such, for instance, as trembling, pallor, sobbing, laughter, &c., for these are attributable to the body only, without any reference to the mind. Lastly, the definitions of the emotions require to be supplemented in a few points; I will therefore repeat them, interpolating such observations as I think should here and there be added.
