"If one demands demonstration of each demonstration, we shall go out to infinity, and thus demonstration is overthrown; but on the other alternative, these very things that are credible of themselves become the first principles of the demonstrations. Indeed the philosophers admit that the first principles of all things are indemonstrable. So that if there is demonstration at all, there is an absolute necessity that there be something credible of itself, which is called first and indemonstrable." (St. Clement of Alexandria, Stromata VIII, c. 3)
Introduction
In the apologetic sphere, Jay Dyer has become quite infamous for his frequent references to “Thomistic Epistemology” when confronted on a variety of seemingly unrelated issues. The claim is made that Thomistic philosophy has no equipment to justify its own first principles.
In order to disarm this objection against Thomism, it is important to properly locate where the Thomistic solution is to be found.
No Science Demonstrates Its Own Principles
According to the Aristotelian-Scholastic tradition, no science demonstrates the first principles from which it draws its conclusions. Each of the sciences does not defend its own first principles, but presupposes them. The reason for this is simple. If a science demonstrates in virtue of its principles. Therefore, if a science demonstrated its first principles, then it would either demonstrate it by the first principle or some principle derived from the first principle. In either case, there would be circularity.
In the beginning of the Physics, Aristotle sets this out clearly, stating that natural philosophy does not dispute with those who deny motion, since the entire science is a study of mobile being. Rather, natural philosophy’s first principles are left to a higher science to defend for it.
Now to investigate whether Being is one and motionless is not a contribution to the science of Nature. For just as the geometer has nothing more to say to one who denies the principles of his science—this being a question for a different science, or for one common to all—so a man investigating principles cannot argue with one who denies their existence... We physicists must take for granted that the things that exist by nature are, either all or some of them, in motion, which is indeed made plain by induction... No man of science is bound to solve every kind of difficulty that may be raised, but only as many as are drawn falsely from the principles of the science: it is not our business to refute those that do not arise in this way—just as it is the duty of the geometer to refute the squaring of the circle by means of segments, but it is not his duty to refute Antiphon’s proof. (Aristotle, Physics I, c. 2)
The question then arises: what about the ultimately first principles? While natural philosophy’s principles are subordinated to a higher science, the ultimate first principles have no higher science to draw from. So what are we to do in this case?
Metaphysics Defends What the Other Sciences Presuppose
Here, the Aristotelian-Scholastic tradition answers that the highest science is unique. Whereas the lower sciences leave the defense of their principles to higher sciences, the highest science is equipped to defend its own principles, although not to (strictly) demonstrate them. Therefore, the treatment of the ultimately first principles is left to the science of Metaphysics, which is the science that studies being as being.
Evidently the inquiry into these also belongs to one science... for these truths hold good for everything that is, and not for some special genus apart from others. And all men use them, for they are true of being qua being, and each genus has being. But men use them just so far as to satisfy their purposes—that is, as far as the genus whose attributes they are proving extends. Therefore, since these truths clearly hold good for all things qua being (for this is what is common to them), he who studies being qua being [i.e., the Metaphysician] will inquire into them too. (Aristotle, Metaphysics IV, c. 3)
It is to be borne in mind, in regard to the philosophical sciences, that the inferior sciences neither prove their principles nor dispute with those who deny them, but leave this to a higher science; whereas the highest of them, namely metaphysics, can dispute with one who denies its principles... (St. Thomas, Summa theologiae I, q. 1, a. 8)
For the other sciences, while they use this first principle, they do not use it in its universal or unrestricted sense. Rather, they use it only insofar as it touches the object of their own science. In that sense, while Metaphysics treats it in an unrestricted and universal sense, the other sciences treat it in a restricted and particular sense:
Although the other sciences use the first principles, they do not use them in their universality, but only in a contracted way. For the geometer does not say, without qualification, that it is impossible for the same thing at once to be and not be, but that it is impossible for a line to be commensurate with another and not commensurate. And the arithmetician, that it is impossible for the same number to be even and not even. (Soncinas, Quaestiones metaphysicales acutissimae, lib. IV, q. 31)
Since the first principle must in some way touch all things, the one studying the most universal science is the one whose task it is to study this problem. Now, the most universal concept is being, since everything is insofar as it exists. Hence, Aristotle explicitly treats this problem against the ancient skeptics in Book IV of the Metaphysics, since Metaphysics studies being as being. For this reason, the classical expositions of this problem are found in the traditional commentaries on Aristotle’s Metaphysics—especially the commentary of St. Thomas on these chapters.
It is for this reason that Metaphysics has a double character. Not only is Metaphysics the highest natural science, since it studies the most universal object in its most abstract degree (being as being), it is also the highest natural wisdom, insofar as it is able to contemplate and defend its own principles and conclusions in light of these principles. For, whereas science seeks to draw conclusions, wisdom seeks to contemplate these principles and the conclusions in light of them:
Wisdom makes use of indemonstrable principles of which there is understanding, not only by drawing conclusions from them, as other sciences do, but also by passing its judgment on them, and by vindicating them against those who deny them. Hence it follows that wisdom is a greater virtue than understanding. (St. Thomas, Summa theologiae I-II, q. 66, a. 5, ad 4)
Owing to the universality of the principles from which it proceeds, wisdom has also the property of reflecting upon principles; it reflects both upon its own principles and upon those of the other sciences, not in such a way as to prove them, but in such a way as to explain and defend them. Wisdom is said to include understanding as well as science because it extends even to the principles whose habitus is called understanding. (The Material Logic of John of St. Thomas, p. 509)
Metaphysics... is wisdom without qualification, as the supreme science of the whole natural order; as such it judges concerning the principles of all the sciences of this order: it explains and defends these principles. This belongs to Metaphysics because its object, in its transcendental universality, embraces under itself the objects of all the other sciences. (Gredt, Elementa philosophiae aristotelico-thomisticae, vol. II, n. 615)
While later philosophers treat this question in their treatments of logic (calling it “major logic” or “criteriology”), the traditional treatment of this question comes under the science of Metaphysics, being called “Defensive Metaphysics” as distinguished from the treatment of being as being, which was called “Ostensive Metaphysics.” Many Thomists of the twentieth century pushed back against this shift in the treatment of the first principle to logic.
Answering the Objector
The objector to “Thomistic Epistemology” would do well to reflect upon these considerations. It is true that, if every science as a whole merely presupposed its principles, then the entire edifice would rest upon a presupposition without any ultimate defense. Yet this is not what we are positing. We posit that every particular science presupposes its principles and relies on a higher science for their defense. This is not a reduction to infinity, because we do hold that there is a science that does not treat being only in a particular mode, but universal being as such—namely, Metaphysics. We concede that even this science does not demonstrate, in the strict sense, its principles (and hence the ultimately first principle), but we deny that this science offers no defense whatsoever of its own principles—and, therefore, of the principles of all the lesser sciences.
This is the role of Defensive Metaphysics, which is not something that was absent from the tradition, but was always present in the tradition’s treatment of Metaphysics, long before Kant or Descartes ever arose to posit their own understanding of these matters.
When these authors treat the first principles, they ask three important questions:
What is the absolutely first principle?
How are these principles acquired?
How are these principles defended?
What Is the First Principle?
In order to commence our investigation of what the first principle is, it is necessary for us to inquire into the meaning of a “first principle.” Like in any investigation, we must inquire after the meaning of terms that is set forth in its nominal definition. There are many principles in each of the sciences from which we draw forth conclusions—what does it mean for a principle (or principles) to be “first”?
The tradition, following Aristotle, lists three conditions a principle must meet in order to be first:
(a) It has to be universally known, so that nobody can make an error about it or fail to know it, since it must be necessary to have any knowledge at all.
(b) It is not merely held on supposition or by common agreement, but truly and absolutely held by all, since what is dependent on supposition or common agreement is dependent on something else, and hence not truly first.
(c) It cannot be acquired by demonstration properly so called, but is natural, because if it were acquired by some demonstration, then whatever principles that demonstration relies on would be prior to it.
As Zigliara points out, these conditions laid out by Aristotle coincide with three conditions that are commonly given by modern philosophers: (a) that it rest on no other principle; (b) that with its removal all other principles collapse; (c) that its admission implies the other principles. (Zigliara, Critica, lib. II, cap. II, a. II)
These three conditions, naturally flowing from the concept of the first principle, are what set us up to identify the first principle, describe how it is acquired, and, lastly, define how it may or may not be defended.
According to the tradition, there is one principle to which this applies: that it is impossible for the same thing to be and not to be at the same time and in the same respect, which is referred to as the “principle of non-contradiction.” This is something that is universally held. The man who affirms anything, by that very affirmation, is excluding the corresponding denial of that affirmation at the same time and in the same respect. If someone affirms “John is tall,” he is, by that very affirmation, excluding the proposition that “John is not tall” if taken at the same time and in the same respect. It is not even possible to think the opposite of this principle, since the very intellectual affirmations rely on it. Those who denied this principle (e.g., Heraclitus) did so merely externally, without their external affirmations conforming to what they truly thought.
Further, this is not a principle that is held on supposition or by common agreement, since the very idea of supposing or commonly agreeing would itself rely on this principle. This follows upon the universality of this principle described above.
Lastly, this is not something acquired by demonstration, since demonstration itself relies on this principle. This is important to highlight. While the objector to “Thomistic Epistemology” critiques it on the grounds that it cannot demonstrate, in the strict sense, the first principle, this is an incoherent objection. It is incoherent both to concede that there are first principles and to demand proof of the first principle, since any such proof would implicitly concede that the principle in question is not really first, but itself relies on prior principles. Those prior principles, in turn, would either rely on further principles for their demonstration (leading to an infinite regress) or would have to be defended in some other way—which is to concede our position.
The Metaphysical and Logical Formulations
Here we should make a quick note. There is both a metaphysical and a logical formulation of the first principle. Metaphysics concerns itself with being as such, whereas logic concerns itself with something called “second intentions.” The former is directly concerned with reality, whereas the latter is indirectly concerned with reality, through logical intentions that exist only in the intellect. Therefore, we can state the “law of non-contradiction” either in a metaphysical mode about being (”it is impossible for a thing to be and not to be,” etc.) or in a logical mode about our intentions concerning being (”it is impossible to affirm and deny,” etc.). The former is about being as such; the latter is about our affirmations about being. Clearly, being is prior to our affirmation about being, and our apprehension of it is prior to our affirmations and negations concerning it. It follows, therefore, that the logical form of the first principle follows upon the metaphysical form, and not the other way around.
Since the operation of the intellect is twofold... in the first operation there is something first which falls in the conception of the intellect, namely that which I call being... And because this principle... depends on the understanding of being... this principle is therefore naturally first in the second operation of the intellect [that of composing and dividing]. (St. Thomas, In IV Metaphysicorum, lect. 6, n. 605)
As Goudin points out, Descartes’s formulation of the first principle (”I think, therefore I am”) is false insofar as it is not absolutely first. (Goudin, Philosophia Thomistica, vol. IV, pt. IV, disp. I, q. 1, a. 1) This formulation supposes that to be (”I am”) and not to be (”I am not”) are not the same, and are contraries repugnant to the same affirmation. This enthymeme supposes the law of non-contradiction as a minor premise—the medium of demonstration. Now, that which demonstrates is prior to that which is demonstrated. Therefore, the law of non-contradiction is prior to the Cartesian first principle.
How Is the First Principle Acquired?
Now that we have identified this principle, we can inquire into how it is acquired. The entire Scholastic tradition understands that our intellectual knowledge begins somehow in the senses. Since we are embodied souls, the mode of knowledge connatural to us is through the senses. Are the senses, then, proper causes of this principle of understanding? Soncinas explains:
The knowledge of the first principle... does not depend on any sensitive knowledge as on a cause contributing something to the being of this knowledge... Yet it is necessary, while the intellect forms the first principle, that some knowledge be actually in the imagination or the cogitative power, so that sensitive knowledge is its cause sine qua non. (Soncinas, Quaestiones metaphysicales, lib. IV, q. 32)
While the senses originate this understanding of the first principle, the very evidence for it does not come from the senses, but from the apprehension of the terms by the intellect under the natural light of reason. The reason is simple: if the senses provided the evidence for the first principle, then the first principle would not be first, but would stand as a conclusion drawn from the senses. Sense knowledge, therefore, is a mere condition for the apprehension of the terms in which we have immediate evidence under the light of natural reason. Further, in that case, the greater would come from the lesser—more certain knowledge from less certain knowledge—which would be repugnant.
In order to give a full account of the beginning of the understanding of the first principle, we must state both the condition for such knowledge (i.e., sense knowledge) and its true and proper cause (i.e., the illumination of the agent intellect apprehending immediately the evidence presented):
The third condition is that it is not acquired by demonstration or by any similar method, but comes, in a sense, by nature to the one having it, inasmuch as it is naturally known and not acquired. For first principles become known through the natural light of the agent intellect, and they are not acquired by any process of reasoning, but by having their terms become known. This comes about by reason of the fact that memory is derived from sensible things, experience from memory, and knowledge of those terms from experience. And when they are known, common propositions of this kind, which are the principles of the arts and sciences, become known. (St. Thomas, In IV Metaphysicorum, lect. 6, n. 599)
But someone could believe that sense alone, or the mere remembrance of singulars, is sufficient to cause intellectual knowledge of principles, as some of the ancients supposed, who did not discriminate between sense and intellect. Therefore, to exclude this, the Philosopher adds that along with sense it is necessary to presuppose such a nature of mind as can not only suffer this—that is, be susceptible of universal knowledge, which indeed comes to pass in virtue of the possible intellect—but can also cause this, in virtue of the agent intellect, which makes things intelligible in act by abstraction of universals from singulars. (St. Thomas, In II Posteriorum Analyticorum, lect. 20, n. 593)
The general outlines of this solution are proposed in common by all the schools, yet there is slight disagreement about a single detail: the role of the senses. Both agree that the immediate evidence for the first principle lies in the apprehension of the terms under the light of the agent intellect. Both agree that the connatural mode in which this knowledge originates is in the senses. Yet the Scotists—following Bl. Scotus—rather than holding that sense knowledge is a necessary condition for such knowledge, argue that the senses are its mere occasion. (Scotus, Ordinatio I, d. 3, pars 1, q. 4) This difference is subtle and should not detain us here, but is important to note.
It is important to note these points with sufficient detail in order to refute those who accuse the Thomistic account of epistemology of being powerless against those who systematically deny the reliability of the senses. Even if, in argumentum, we conceded that sense data was unreliable, it would not matter, because the evidence for the first principle does not come from the sense data as such, but from the apprehension of terms that merely supposes the senses originatively. Even if our senses were completely unreliable, our intellect would still sufficiently apprehend the evidence for the first principle under the light of the agent intellect, and would still be able to form the habit of understanding.
The principle of non-contradiction is a principle about being. Therefore, we acquire it in the way that we are able to come to understand being. We interact with being through the senses, and our intellect is then able to understand things in this way, abstracting from the impressions of the senses. Therefore, we hold that the evidence for this principle comes to us immediately by our apprehension of being, which begins in the senses according to its connatural mode. Whereas the knowledge of other things may come by reasoning from premise to conclusion, the evidence for this principle is immediate, and comes to us by a direct apprehension of being. Hence, the apprehension of being (in the first operation of the intellect) precedes and necessarily induces the first principle (in the second operation of the intellect), which judges that what is apprehended is not what is not apprehended. This is not as a second intention (which would be the logical formulation mentioned above), but as a direct apprehension of being, and therefore as a metaphysical principle. This follows from what was said above: the first principle must be natural rather than demonstrated, and it must be about being, since the first principle must be the most universal, and being is the most universal thing—the object of all thinking and of every proposition:
That which, before aught else, falls under apprehension, is being, the notion of which is included in all things whatsoever a man apprehends. Wherefore the first indemonstrable principle is that the same thing cannot be affirmed and denied at the same time, which is based on the notion of being and not-being; and on this principle all others are based... (St. Thomas, Summa theologiae I-II, q. 94, a. 2)
The origin of this principle, as we have stated many times, comes through the objective apprehension that is natural to the process of intellection. While other principles may come by demonstration, and be seen in light of higher principles, the sole criterion for the first principle is the immediate evidence inherent in intellection. This process terminates in what the tradition calls “understanding,” which is the habit of first principles. Understanding apprehends the first principles; wisdom explains, contemplates, and defends them; science draws necessary conclusions from them. If one mixes any of these together, one falls into grave error—just as the man who demands a strict demonstration of the first principles (a function of science), when he should really be asking for their explanation and defense (a function of wisdom). If a man seeks evidence for the first principle either in wisdom or in science, he errs, since the immediate evidence for it comes by way of understanding.
How Is the First Principle Defended?
All of this is simply preliminary to our last consideration. This principle is accepted by all and comes to us naturally—but how is it defended? It is clear that it cannot be demonstrated strictly, since any demonstration would assume the very principle it seeks to demonstrate. This would be an instance of begging the question. From this fact, many skeptics have concluded that the principle is without evidence or defense. This is the wrong conclusion to draw. As Aristotle teaches, this is a desire that proceeds from a lack of education:
Some indeed demand that even this shall be demonstrated, but this they do through want of education, for not to know of what things one should demand demonstration, and of what one should not, argues want of education. For it is impossible that there should be demonstration of absolutely everything (there would be an infinite regress, so that there would still be no demonstration); but if there are things of which one should not demand demonstration, these persons could not say what principle they maintain to be more self-evident than the present one. (Aristotle, Metaphysics IV, c. 4)
We have already indicated where the objective evidence for this principle comes from: the very understanding of being that begins in the senses.
Yet the second half of the question is properly considered here. How are we to defend the first principle? Obviously not through any sort of direct argument or demonstration, since this would assume what it seeks to prove. How, then? The Aristotelian-Scholastic tradition answers that there are three ways to defend this principle indirectly: an “expository” manifestation, a reduction to absurdity, and a solution of objections.
In this way, Metaphysics also differs from the lower sciences. The lower sciences presuppose and “take” their first principles from higher sciences (although, as stated above, only in a restricted sense); Metaphysics, on the other hand, is able truly to defend the absolutely first principle, and to give this first principle to the lesser sciences for their use:
The first philosopher considers the first principles not only by presupposing them, as the particular sciences do, but also by demonstrating. Yet it is not thereby required that he demonstrate them simpliciter; it suffices that he demonstrate the errors concerning them, arguing from things less known and conceded by the adversary, and by clarifying the terms—which does not belong to the particular sciences. (Dominic of Flanders, In XII libros Metaphysicae Aristotelis quaestiones, lib. IV, q. VI, a. 1, ad 3)
First Mode: The Expository Manifestation
First, there is the expository manifestation, where the truth of the principle is shown by an explanation of its terms (called “imperfect illation”), described as an “analysis and explanation of terms.”
This first defense follows from what was explained above about the first principles forming a habit called “understanding.” If we truly gather the first principles from our ordinary process of intellection, and immediately have evidence of them in our very apprehension of being—forming a habit from this process—then it follows that we are able to defend these first principles by a simple explanation of the terms in the proposition. If these terms are explained in such a way as to show that the subject and predicate are identical, then it follows necessarily that the affirmation is true; the same applies to negation, but in the opposite direction.
As St. Albert the Great says, “everyone who knows what affirmation is and what negation is, knows that of anything whatever the affirmation or the negation is true.” (St. Albert the Great, In I Posteriorum Analyticorum, tr. II, c. 6) It is called an “expository syllogism” because we are simply explaining and unfolding what is already explicitly contained in the terms of the proposition, rather than exercising demonstration. This, therefore, does not violate the principle that the first principle is indemonstrable, but it does provide a defense of it.
The reason for this is that the terms of the first principle are self-evident and universal. Therefore, in order to defend them, one merely needs to manifest the connection between the subject and predicate by explanation:
If the self-evident proposition is considered in positive fashion, it is defined as “a proposition known by reason of the terms themselves, or by the explanation of the terms.”... A proposition is self-evident in itself when there is immediate connection in the object, and it is self-evident to us when this connection is manifested and explained by terms of such a nature that, without discourse and by the mere understanding of the terms, we come to know the connection. (The Material Logic of John of St. Thomas, pp. 461–464)
Second Mode: The Reduction to Absurdity
Second, there is the reduction to absurdity, where the truth of the principle is shown by drawing out the consequences of its denial. Any man we speak to who affirms or denies anything—even affirmations or denials about the first principle itself—affirms the first principle, even implicitly. Therefore, we can reduce such a denial of the first principle to absurdity. What are we to do if he refuses to affirm or deny anything at all? Aristotle says that such a man is no better than a vegetable:
We can, however, demonstrate negatively even that this view is impossible, if our opponent will only say something; and if he says nothing, it is absurd to seek to give an account of our views to one who cannot give an account of anything, in so far as he refuses to do so; for such a man, as such, is from the start no better than a vegetable. (Aristotle, Metaphysics IV, c. 4)
If he says nothing, it is ridiculous to look for a reason against one who does not make use of reason in speaking, for in this dispute anyone who signifies nothing will be like a plant, for even brute animals signify something by such signs. (St. Thomas, In IV Metaphysicorum, lect. 6, n. 608)
According to Avicenna, the man who denies the first principle should be beaten and burned until he admits that it is something different to be beaten than to be not-beaten and burned than to be not-burned. There is a remedial function of these various arguments, which are meant to induce the intellect of the hearer to consider the absurdity of his denial of the first principle.
This is not a begging of the question, because we do not begin with the demand that such a person affirm or deny anything, but with the fact that he does affirm or deny something, even if it merely concerns the first principle. In fact, the very demand itself places the burden of proof on the one making it, since the demand is itself an act of reason, which already implies the first principle.
The starting-point for all such arguments is not the demand that our opponent shall say that something either is or is not (for this one might perhaps take to be a begging of the question), but that he shall say something which is significant both for himself and for another; for this is necessary, if he really is to say anything... The person responsible for the proof, however, is not he who demonstrates but he who listens; for while disowning reason he listens to reason. (Aristotle, Metaphysics IV, c. 4)
In other words, when a process of this kind, from a less well-known to a better-known principle, is employed for the sake of convincing another man who denies this, there will then be disproof or refutation, but not demonstration—that is, it will be possible to have a syllogism which contradicts his view, since what is less known absolutely is admitted by the opponent, and thus it will be possible to proceed to demonstrate the above-mentioned principle so far as the man is concerned, but not in the strict sense. (St. Thomas, In IV Metaphysicorum, lect. 6, n. 610)
It is for this reason that the tradition often calls this demonstration “redargutive,” since it proceeds on the basis of something conceded by the objector, rather than proceeding from something necessary and more universal (which would be a proper demonstration, and therefore impossible in this case, since we are considering the first principle):
Absolute demonstration differs from redargutive in this: the absolute is from things more known simpliciter; the redargutive is from things conceded by the adversary, less known simpliciter, but more known to the adversary himself. From this I prove the conclusion: he who denies this principle... can be led to some absurdity more known to himself than the first principle; therefore it can be demonstrated redargutively. (Javellus, Quaestiones super IV Metaphysicae, q. X)
It is based on the very act of signification posited by the objector, even where that act of signification is itself a denial of the very principle. It is the very act of speaking and signifying that Aristotle latches onto in the Metaphysics. We do not argue (which would be circular) on the basis of whether or not what the opponent says is true or not. Rather, we argue on the basis of their very speaking. Insofar as they speak, they have already assumed that speech signifies something, which he is destroying by his denial of the principle.
He who acknowledges a determinate sense in a determinate word, by that very fact confesses that this word and this sense are distinguished from their contradictory. But to admit this is to assert the principle of contradiction. Therefore the skeptic cannot seriously attack the truth of the principle of contradiction without by that very fact professing it. (Hugon, Logica Maior, tr. II, q. II, art. 1)
But neither can the skeptic propose his own system; indeed, he cannot say a word without contradicting himself. For if he intends to signify something by his words, he already distinguishes what he intends from its contradictory; hence he must be said to admit the principle of contradiction. (Gredt, Elementa philosophiae aristotelico-thomisticae, vol. II, n. 674)
This is also called an argument ad hominem—which is different from the fallacy ad hominem—insofar as one is arguing on the basis of something conceded by the adversary (sometimes called an “internal critique”).
Third Mode: The Solution of Objections
Third, there is the solution to objections, called the “negative office.” This negative office does not receive a systematic treatment in the tradition, because none can be had. It is, rather, something occasional: one hears the objections to the first principle and either shows them to be false or, at least, shows them not to be necessary. (St. Thomas, Summa theologiae I, q. 1, a. 8; Super Boetium de Trinitate, q. 2, a. 3)