Ética, Parte V, Proposición 9

An emotion is only bad or hurtful, in so far as it hinders the mind from being able to think (IV. xxvi. xxvii.); therefore, an emotion, whereby the mind is determined to the contemplation of several things at once, is less hurtful than another equally powerful emotion, which so engrosses the mind in the single contemplation of a few objects or of one, that it is unable to think of anything else; this was our first point. Again, as the mind's essence, in other words, its power (III. vii.), consists solely in thought (II. xi.), the mind is less passive in respect to an emotion, which causes it to think of several things at once, than in regard to an equally strong emotion, which keeps it engrossed in the contemplation of a few or of a single object: this was our second point. Lastly, this emotion (III. xlviii.), in so far as it is attributable to several causes, is less powerful in regard to each of them. Q.E.D.