Having dealt with the truth in Q16, it’s entirely natural that Aquinas should enquire into falsehood in this question. What is it? Where does it exist? and what relation does it have with the truth?
The Thread of the Argument
A1: Aquinas first asks whether falsity exists in things much in the same way as he asked whether truth existed in things or in the intellect in Q16. He affirms that truth and falsity are opposed to one another and that as truth is found primarily in the intellect, we must look there first for falsehood. Similarly, things will be called false in an absolute sense where their existence depends per se (that is, for their very being) on an intellect. For natural things, the intellect concerned is God’s intellect. Now, although we might call an artefact (something we make for a purpose) false if it were a bad example of an artefact, we cannot say the same in the case of things that God makes as He makes them according to the ordination of His intellect (and He makes them as He makes them, however perplexing that may be to us). There is no falsehood in the intellect of God. (Aquinas deals separately with the case of creatures to whom He has given free will and who may sin against His will). But as far as our intellect is concerned, natural things are related per accidens, and although we therefore cannot call them false in an absolute sense, we can call them false in a derived sense. Aquinas identifies two ways in which we can attribute falsity to natural things in this derived fashion. Firstly something can be false with respect to what fails to exist in it (a great tragic actor would make a poor heroic character) and secondly in the sense that it can deceive us as to what it truly is.
A2: Next Aquinas asks whether falsity can exist in the senses. It might seem that falsity can only exist in the interpretation of our sense data rather than in the sense data themselves (as they simply exist prior to interpretation). But Aquinas takes a different view. He says that falsity should be looked for in the senses only to the extent that truth exists in them, so that we can only say that falsity exists in the senses when they apprehend things otherwise than they actually are (so that a false likeness of a thing is produced). He identifies three ways in which likenesses of things exist in the senses: primarily and substantially (such as colour sensations), called “proper sensibles”; secondarily and substantially (such as shape or magnitude sensations), called “common sensibles”; and secondarily and accidentally (such as the sensation of a particular individual thing like a man). He seems to be arguing that senses can operate in more ways that simply the apprehension of primary sensations. They are capable of “pre-processing” primitive sense data before it is presented to the intellect. Therefore falsehood can exist in the first of these only when the sense organ itself is not working properly but can occur in the others when the senses make mistakes in this pre-processing.
A3: We might be tempted to claim that since truth exists primarily in the intellect, we can immediately infer that falsity exists primarily in the intellect. But deception might give an example where falsehood occurs as a privation of understanding, so how can one say that the falsehood exists in the intellect (rather than the truth failing to exist)? In order to address the question of whether falsity exists in the intellect, Aquinas has to enquire into how the intellect might fail. In order to do this he makes a number of parallels. A thing, such as a human, is a composite of form and matter. It is quite possible for that thing to be defective in a number of possible ways; for example a human may be born with only one leg. But that human being is still a human being. It is of the nature of human beings to be two-legged; being two-legged follows on from being a human (in Aristotelian terms it is a “property” of being human). But our human being cannot be defective with respect to the being he or she derives from his or her form; their form (the soul) gives them their essential humanity. If they were defective with respect to this, they would simply not be human beings in the first place but some other sort of being. Similarly, as we saw in article 2, sense organs cannot be “false” in sensing proper sensibles (they simply sense what they sense). In a parallel manner, the first operation of the intellect (see below) is to grasp the quiddity (the “what-ness”) of things; in this, the intellect cannot be deceived as to the quiddity of something. (The intellect is simply informed by the form that it receives; “either it is true or it understands nothing at all”. We’ll hear more about this in Q85.) However, it can be deceived when it starts thinking about this quiddity and can get completely the wrong end of the stick about the thing itself. So, in one sense (in its first operation) the intellect contains no falsity; but it may contain falsity reflecting upon the quiddity it has received. It may also be deceived in identifying what it has perceived: it may simply get the wrong identification; or it may put together incommensurable definitions to end up with nonsense.
A4: In the fourth article, Aquinas asks us to consider the relationship between truth and falsity. One might wish to say they are simply opposites, but Aquinas wishes to be precise about what this means. To do this he runs though a number of possible relationships. We might first think of the idea of “negation”. When we say that something is “not-black” we simply deny that the thing is black. Strictly speaking we say nothing positive about it at all (we might be inclined to think that “not-black” implies some other colour, but this is not necessarily so); negation tells us nothing positive about the subject, it simply denies something. On the other hand, a “privation” tells us about some element missing in something the nature of which it is to have that element. (So “blindness” tells us about something missing in something whose nature it is to see.) A privation determines a subject. Lastly, a “contrary” both determines a subject and tells us something positive about it. For example, “white” is a contrary to “black. Although one might be inclined to think that falsity is a privation of the truth (as evil is the privation of good), Aquinas, following Aristotle, claims that falsity is a contrary to truth because a falsehood posits a definite belief that does not correspond to its subject.
- As we’ve seen before. Aquinas understands the intellect as composed of an active (agent) part and a passive part. He also sees the operation of the intellect divided into two. The first act of the intellect (also called simple apprehension) is that by which the intellect knows what a thing is (its quiddity) without affirming or denying anything of it. The second operation of the intellect (also known as judgement) involves the intellect affirming or denying things of it by a process of composing or dividing. It is in the second operation of the intellect that we grasp the being (the esse) of something.
- Aquinas also divides the operation of the senses into the apprehension of “proper sensibles” that are the basic sense data from each individual sense organ (i.e. so colour is proper to the sense of sight) and “common sensibles” that are those things apprehended by more than one sense organ. (Movement, for example can be seen and felt). He calls these two “per se” (or substantial). He also identifies “per accidens” (“accidental”) objects of the senses that correspond to what you or I might think of “things” like a bowl of sugar. For a bowl of sugar, the per se objects of the senses are things like the colour, the shape, the size and so forth; the accidental object of the senses is the complex of these things assembled as a complex (but prior to apprehension of its quiddity by the intellect).
- Aquinas assumes quite a lot of Aristotelian psychology in this question without explaining it in much detail. He comes back for a fuller treatment in the “Treatise on Man” in Questions 75-102 of the first part.