E4P9D
Demonstration — Part IV
Latin
Imaginatio est idea qua mens rem ut præsentem contemplatur (vide ejus definitionem in scholio propositionis 17 partis II) quæ tamen magis corporis humani constitutionem quam rei externæ naturam indicat (per corollarium II propositionis 16 partis II). Est igitur affectus (per generalem affectuum definitionem) imaginatio quatenus corporis constitutionem indicat. At imaginatio (per propositionem 17 partis II) intensior est quamdiu nihil imaginamur quod rei externæ præsentem existentiam secludit; ergo etiam affectus cujus causam in præsenti nobis adesse imaginamur, intensior seu fortior est quam si eandem non adesse imaginaremur. Q.E.D.
English (Elwes 1883)
Imagination or conception is the idea, by which the mind regards a thing as present (II. xvii. note), but which indicates the disposition of the mind rather than the nature of the external thing (II. xvi. Coroll. ii.). An emotion is therefore a conception, in so far as it indicates the disposition of the body. But a conception (by II. xvii.) is stronger, so long as we conceive nothing which excludes the present existence of the external object; wherefore an emotion is also stronger or more intense, when we conceive the cause to be with us at the present time, than when we do not conceive the cause to be with us. Q.E.D.
Modern English
Imagination is the idea by which the mind regards a thing as present (E2P17S), though it indicates the constitution of the human body rather than the nature of the external thing (E2P16C2). An affect is therefore (E3DA49) an imagination insofar as it indicates the body's constitution. But an imagination (E2P17S) is more intense so long as we imagine nothing that excludes the present existence of the external thing. An affect whose cause we imagine as present with us now is therefore more intense — that is, stronger — than if we did not imagine the cause as present. Q.E.D.