E4P1S
Scholium — Part IV
Latin
Intelligitur hæc propositio clarius ex II corollario propositionis 16 partis II. Nam imaginatio idea est quæ magis corporis humani præsentem constitutionem quam corporis externi naturam indicat, non quidem distincte sed confuse; unde fit ut mens errare dicatur. Exempli gratia cum solem intuemur, eundem ducentos circiter pedes a nobis distare imaginamur, in quo tamdiu fallimur quamdiu veram ejus distantiam ignoramus sed cognita ejusdem distantia tollitur quidem error sed non imaginatio hoc est idea solis quæ ejusdem naturam eatenus tantum explicat quatenus corpus ab eodem afficitur adeoque quamvis veram ejusdem distantiam noscamus, ipsum nihilominus prope nobis adesse imaginabimur. Nam ut in scholio propositionis 35 partis II diximus, non ea de causa solem adeo propinquum imaginamur quia ejus veram distantiam ignoramus sed quia mens eatenus magnitudinem solis concipit quatenus corpus ab eodem afficitur. Sic cum solis radii aquæ superficiei incidentes ad nostros oculos reflectuntur, eundem perinde ac si in aqua esset, imaginamur tametsi verum ejus locum noverimus et sic reliquæ imaginationes quibus mens fallitur, sive eæ naturalem corporis constitutionem sive quod ejusdem agendi potentiam augeri vel minui indicant, vero non sunt contrariæ nec ejusdem præsentia evanescunt. Fit quidem cum falso aliquod malum timemus, ut timor evanescat audito vero nuntio sed contra etiam fit cum malum quod certe venturum est, timemus ut timor etiam evanescat audito falso nuntio atque adeo imaginationes non præsentia veri quatenus verum evanescunt sed quia aliæ occurrunt iis fortiores quæ rerum quas imaginamur, præsentem existentiam secludunt, ut propositione 17 partis II ostendimus.
English (Elwes 1883)
This proposition is more clearly understood from II. xvi. Coroll. ii. For imagination is an idea, which indicates rather the present disposition of the human body than the nature of the external body; not indeed distinctly, but confusedly; whence it comes to pass, that the mind is said to err. For instance, when we look at the sun, we conceive that it is distant from us about two hundred feet; in this judgment we err, so long as we are in ignorance of its true distance; when its true distance is known, the error is removed, but not the imagination; or, in other words, the idea of the sun, which only explains tho nature of that luminary, in so far as the body is affected thereby: wherefore, though we know the real distance, we shall still nevertheless imagine the sun to be near us. For, as we said in II. xxxv. note, we do not imagine the sun to be so near us, because we are ignorant of its true distance, but because the mind conceives the magnitude of the sun to the extent that the body is affected thereby. Thus, when the rays of the sun falling on the surface of water are reflected into our eyes, we imagine the sun as if it were in the water, though we are aware of its real position; and similarly other imaginations, wherein the mind is deceived, whether they indicate the natural disposition of the body, or that its power of activity is increased or diminished, are not contrary to the truth, and do not vanish at its presence. It happens indeed that, when we mistakenly fear an evil, the fear vanishes when we hear the true tidings; but the contrary also happens, namely, that we fear an evil which will certainly come, and our fear vanishes when we hear false tidings; thus imaginations do not vanish at the presence of the truth, in virtue of its being true, but because other imaginations, stronger than the first, supervene and exclude the present existence of that which we imagined, as I have shown in II. xvii.
Modern English
This proposition is understood more clearly from Corollary II to Proposition 16 of Part 2 (E2P16C2). For imagination is an idea that indicates the present state of the human body more than the nature of the external body — not distinctly, but confusedly. This is why the mind is said to err.
For example, when we look at the sun we imagine it to be about two hundred feet away. In this we are mistaken as long as we do not know the sun's true distance; but once we know that distance, the error is removed — yet the imagination is not. That is, the idea of the sun, which explains its nature only insofar as the body is affected by it, persists; so even knowing the true distance, we will still imagine the sun as nearby. For, as we said in the Scholium to Proposition 35 of Part 2 (E2P35S), we do not imagine the sun so close because we are ignorant of its true distance, but because the mind conceives the sun's magnitude only to the extent that the body is affected by it.
Similarly, when the sun's rays strike the surface of water and are reflected back to our eyes, we imagine the sun as if it were in the water, even though we know its true position. And likewise the other imaginations by which the mind is deceived — whether they indicate the natural constitution of the body or something that increases or diminishes its power of acting — are not contrary to what is true, and they do not disappear when the truth is present.
It does happen that when we mistakenly fear some bad thing, the fear vanishes when we hear the true report. But the reverse also happens: we fear a bad thing that will certainly come, and the fear vanishes when we hear a false report. So imaginations do not vanish in the presence of truth insofar as it is true, but because other imaginations, stronger than the first, arise and exclude the present existence of what we were imagining — as we showed in Proposition 17 of Part 2 (E2P17).