B. Against the Opinion in Itself

229. As to the second article [n.218], in order for the error of the academics to have no place in any knowables, one needs to see how one should speak about the three aforesaid knowables [nn.224-228] - namely about principles known per se and conclusions, and second about things known through experience, and third about our own acts - whether it be possible for infallible certitude of them to be possessed.

230. [About the knowledge of principles and conclusions] - As to certitude about principles, then, I say as follows: the terms of principles known per se have such an identity that the one includes the other with evident necessity, and so the intellect, combining the terms from the fact it apprehends them, has in itself the necessary cause of the conformity of the act of combining with the terms themselves of which it is the combining, and has also the evident cause of such conformity; and so to it is necessarily plain the conformity whose evident cause it apprehends in the terms. Therefore, the intellect cannot have an apprehension of the terms, and a combining of them, without there being a conformity of that combining with the terms, just as a white thing and a white thing cannot be without a likeness being between them. Now this conformity of the combining with the terms is the truth of the combining; therefore, the combining of such terms cannot be without being true, and so the perception of the combining and the perception of the terms cannot be without perception of the conformity of the combining with the terms, and so without perception of the truth, because the first perceived things evidently include the perception of this truth.

231. This reason is confirmed through a likeness, from the Philosopher Metaphysics 4.3.1005b29-32, where he maintains that the opposite of a first principle cannot arrive in anyone’s intellect, namely the opposite of this principle ‘it is impossible for the same thing to be and not to be’, “because then contrary opinions would exist in the mind together;” because it is, of course, true of contrary opinions, that is, of opinions formally repugnant, that an opinion opinining ‘it is’ of something and an opinion opining ‘it is not’ of the same thing are formally repugnant.

232. So I assert, in the issue at hand, some repugnance of understandings in the mind, though not formal repugnance. For if knowledge of whole and part stands in the intellect, and the combining together of them, then, since these include, as by necessary cause, the conformity of the combining with the terms, if the opinion stand in the intellect that this combining is false, cognitions will stand that are repugnant, not formally, but one cognition will stand with another and yet it will be the necessary cause of a cognition opposite to it, which is impossible. For just as it is impossible for white and black to stand together (because they are contraries formally), so is it impossible for white to stand together with what is precisely cause of black, thus necessarily cause, because unable, without contradiction, to be without it [sc. black].

233. When certitude about first principles is possessed [nn.230-232], it is plain how it will be possessed about conclusions inferred from them, on account of the evidence of the form of a perfect syllogism; for the certitude of the conclusion depends only on the certitude of the principles and on the evidence of the inference.

234. But will the intellect really not err in this knowledge of principles and conclusions, if all the senses are deceived about the terms?

I reply that, as far as concerns this knowledge, the intellect does not have the senses as cause but only as occasion. For the intellect can have of simples only knowledge received from the senses, but, once the knowledge is received, it can by its own virtue combine the simples together. And if by reason of such simples the combination of them is evidently true, the intellect will by its own virtue and by virtue of the terms assent to the combination - not by virtue of the senses from which it exteriorly gets the terms. An example: if the idea of ‘whole’ and the idea of ‘being greater’ is received from the senses, and if the intellect put together this proposition, ‘every whole is greater than its part’, the intellect will by its own virtue and by that of these terms assent indubitably to this combination, and will not just do so because it saw the terms conjoined in reality (the way it assents to this complex, ‘Socrates is white’, because it sees that these are united in reality). Indeed, I say that if all the senses from which such terms are received were false, or if (and this counts more for deception) some senses were false and some were true, the intellect would not be deceived about such principles, because it would always have in itself the terms that were cause of the truth; as suppose that on someone born blind were miraculously impressed in a dream the species of white and black, and suppose these species remained afterwards when he was awake, his intellect by abstracting would combine from them this proposition, ‘white is not black’, and about it his intellect would not be deceived although the terms were received from erring sense; for the formal idea of the terms, which has been reached, is the necessary cause of the truth of this negative proposition.

235. [About knowledge through experience] - About the second knowables, namely things known through experience [n.229], I say that although experience not be of all singulars but of many, nor always but often, yet someone with experience does infallibly know that so it is both always and in all things, and this through this proposition residing in the soul, ‘whatever comes about for the most part from a non-free cause is the natural effect of that cause’. This proposition is known to the intellect even had it taken its terms from erring sense, because a non-free cause cannot produce non-freely an effect for the most part, the opposite of which it is ordered to, or which it is not ordered to by its form. But a chance cause is ordered to producing the opposite of a chance effect or to not producing it; therefore nothing is a chance cause of an effect that is frequently produced by it, and so, if it is not free, it will be the natural cause.a And this effect comes about from the cause for the most part; this is taken from experience. For, after finding such a nature now with this sort of accident now with that, what is found is that, however great the diversity of accidents, always was such effect consequent to this nature. Therefore, the effect did not follow some accident of this nature, but from the nature itself in itself did such effect follow.

a.a [Interpolated text - in place of “therefore nothing.. .natural cause”] therefore it is a natural cause of an effect frequently produced by it, because it is not a chance cause.

236. But further to be noted is that sometimes experience is had of a conclusion, as that the moon is frequently eclipsed, and then, on the supposition of the conclusion that so things are, a cause of this conclusion is looked for by way of division. And sometimes from experiencing the conclusion one reaches principles known from the terms. And then, from such a principle known from the terms can the conclusion, known previously only by experience, be known more certainly, namely with the first kind of knowledge, because known as deduced from a principle known per se [nn.229-230] - the way this is per se known, that ‘a dark body interposed between a manifest body and the light is preventing the multiplication of the light to such manifest body’. And if it has been found by division that the earth is such a body interposed between the sun and the moon, this will be known most certainly by a demonstration ‘because of which’ (because through the cause), and not only by experience in the way this conclusion was known before the finding of the principle.

237. Now sometimes there is experience of a principle, so that it is not possible to find by way of division a further principle known from the terms, but a stand is made in something true for the most part, whose extreme terms are known by experience to be frequently united, for example that this plant of this sort of species is hot. And there is no prior middle term found whereby the property may be proved of the subject by a demonstration ‘because of which’, but a stand is made in this as in something that is on account of experiences a first known. Although then uncertainty and fallibility may be removed by this proposition, ‘an effect for the most part of a non-free cause is the natural effect of it’, yet this is the last degree of scientific knowledge. And perhaps in that case actual knowledge is not had of the union of the extreme terms, but aptitudinal knowledge. For if the property is some absolute thing other than the subject, it could be separated from the subject without contradiction, and the experienced person would not have knowledge that it is so, but that it is apt to be so.

238. [About our acts] - About the third knowables, namely our own acts [n.229], I say that there is certitude about many of them, as there is of things known first and per se, as is plain from Metaphysics 4.6.1011a3-9, where the Philosopher says of the arguments of those who say that all appearances are true, because those arguments ask “whether we are now awake or sleeping; and all such doubts have the same effect; for they make it an axiom that there is a reason for everything.” And he adds, “they are asking for a reason for things of which there is no reason, for there is no demonstration of a principle of demonstration.” So, for Aristotle there, ‘we are awake’ is known per se like a principle of demonstration; nor is it an objection that it is contingent because, as was said elsewhere [Ord. Prol. n.169], there is an order in contingent things, for some of them are first and immediate, else there would be a process to infinity in contingent things, or something contingent would follow from a necessary cause, both of which are impossible.

239. And just as there is certitude about being awake as about something known per se, so also about many other acts that are in our power (as that I understand or I am hearing), and about others that are perfect acts. For although there is no certitude that I am seeing a white thing located outside, or in such a subject or at such a distance, because an illusion can occur in the medium or in the organ and in many other ways, yet there is certitude that I am seeing, even if there is illusion in the organ. And this seems most of all to be an illusion, namely when, without an object being present, an act in the organ arises of the sort that is of a nature to arise in the presence of an object. And so if the power had its own action when such a condition is posited, that which would be called vision would truly be there, whether it be an action or a passion or both. But if an illusion were to happen, not in the organ proper, but in something close to it that the organ seems to be -as that if an illusion were not to occur in the bundle of the nerves, but that in the eye itself an impression were to arise of the sort of species that is of a nature to arise from a white thing - still the eye would be seeing, because such a species, or what is of a nature to be seen in it, would be seen. For it has distance enough as regard the organ of sight that is in the bundle of the nerves, as appears in Augustine On the Trinity 11.3 n.4, that the reliquies of things seen remaining in the eye are seen with the eyes closed; and in the Philosopher On Sense and Sensed Object 2.437a23-26, it appears that the fire [the ‘flash’] which is generated from a violent upward raising of the eye and reduplicated is seen until the eyelids are shut. These are true seeings, though not the most perfect ones, because there are here sufficient distances from the species to the principal organ of sight.

240. But how is certitude had of things that are subject to the acts of sense, as that something outside is the sort of white or hot that appears?

I reply:

Either the same things about such an object appear opposite to diverse senses, or they do not, but all the senses that know it have the same judgment about it.

241. If in the second way, then certitude of the truth is had of this sort of thing known through the senses and through this proposition from before [n.235], that ‘what is brought about for the most part by something, that something is the natural cause of it, provided it not be a free cause’. Therefore, when this something is present and from it this sort of change arises in the senses for the most part, it follows that the change, or the generated species, is the natural effect of such a cause; and so such thing outside will be white or hot, or some other such thing as is of a nature to be presented through the species that is for the most part generated by it.

242. But if diverse senses have diverse judgments about something seen outside, as that sight says a stick part of which is in water and part in the air is broken, that sight always says the sun is of less size than it is, and that everything seen from a distance is smaller than it is - in such things there is certitude about what is true, and about which sense is erring, through a proposition resting in the soul that is more certain than any judgment of the senses, and through the acts coming together of several senses; so that always some proposition sets the intellect right about the acts of the senses, about which is true and which is false; and in this proposition the intellect does not depend on the senses as on a cause, but as on an occasion.

243. An example. The intellect has this proposition resting in it, ‘no thing that is rather hard is broken by touching something soft that yields to it’. This is so per se known from the terms that, even if the terms were taken from the senses, the intellect cannot doubt of it; indeed, the opposite includes a contradiction. But that the stick is harder than water and that water yields to it, this each sense states, both sight and touch. It follows, therefore, that the stick is not broken as the senses judge it broken; and so which sense errs and which does not about the breaking of the stick, the intellect judges through something more certain than every act of the senses.

244. Similarly, on the other part [sc. the size of the sun, n.242], the fact that a quantity placed altogether against a quantity is equal to it, this is known to the intellect however much the knowledge of the terms be taken from an erring sense; but that the same quantity could be placed against something seen near at hand and far off, this both sight and touch say; therefore the quantity is equal whether seen near at hand or far off; therefore the sight when saying it is smaller is in error.

245. This conclusion [n.244] is proved from principles known per se, and from the acts of two senses that know that so things are for the most part. And so, whenever reason judges the senses to be erring, it judges this not through any knowledge precisely acquired from the senses as from the cause, but through some knowledge occasioned by the senses, in which it is not deceived even if all the senses are deceived [n.234], and by some other knowledge, acquired from a sense or senses, that is ‘for the most part’, and these are known to be true by the proposition often cited [nn.235, 237, 241, added note to n.228], namely that ‘what is brought about for the most part etc.’a

a.a [Interpolated note] - But note that if all the senses erred about all sensible objects common to all the senses [cf. Ord. Prol. n.33] (for example about figure, quantity, or about this figure or this quantity, or that one thing was two, or that this one thing, as a head, was two heads), then the intellect could not have any certitude about it from the senses, by the fact all the senses are erring -or because each sense is erring about its own proper object; and this happens in two ways, either about this color or that, or about a white or black thing. In the first way the sense is not in error about its first object, and so neither is the intellect; but if the sense is deceived about a secondary object, as sight [about a white or black thing], Sensibles are typically divided into proper sensibles, which belong to one sense only (color proper to the eyes, sound to the ears, etc.), common sensibles, which are common to more than one sense (as shape, size, number), and accidental sensibles, which are perceived immediately with the proper or common sensibles but are not as such sensible (as that this black thing is Cuddles the cat, or that white thing is Snowy the poodle). Senses cannot be deceived about proper sensibles but can be about common and accidental sensibles. The ‘secondary object’ mentioned here, about which deception is possible, is primarily, one assumes, a reference to the accidental sensibles, since the common sensibles have just been discussed earlier in this note. The point, then, seems to be that if someone is deceived as to all accidental sensibles, as to whether this black or white thing (or anything with any color between the extremes of white and black or, by extension, anything identified by any sensible proper to any of the five senses) is a cat or a dog or is this cat or some other cat, then the intellect will have no certainty. If it has certainty it will only be in some other person who is not so deceived. ³⁸and then either all sight is deceived about such secondary object, and then there can be no certain knowledge in the intellect, or some sight is deceived and some not, and then [the intellect] can have certitude in another individual, though not in this one.