Why Aristotle’s Chemistry Lasted So Long


In a contemporary introductory chemistry lecture, one can easily imagine—or watch—the professor praising the heroic Democritean insights into void and being—where being consists of the the in-divisible, a-tomic—and lambasting the Aristotelian theory of the four elements (earth, air, fire, and water), which fundamental essences lead to the “compounds” insofar as proximate pairs can be combined (the hot, the cold, the wet, and the dry). (This is not limited to chemists: Richard Feynman himself opens his famous lectures on physics with a hypothetical civilization-ending cataclysmic event and proposes Democrateanism as the central core of knowledge to preserve.)

(image: WikiMedia Commons)

One can then as easily imagine the professor quickly dissecting the claims to fundamentality present in this sketch of Aristotle’s theory. The good professor goes on to lament that—despite its falsity—Aristotelian chymistry went on to hold succeeding generations of thinkers in thrall for centuries. Apart from the usual (and usually grossly oversimplified) explanations for this intellectual enslavement, one might ask the following question:

Is there a good reason for why Aristotle’s approach was the dominant one for so long?

By a good reason, we mean that it would hold true as a reason even today.

• The Desire for A Deep Theory

Let’s work from the idea that Aristotle’s is a “principle” theory, whereas Democritus is proposing a ”constructive” theory. Here we borrow—in an approximate way—Einstein’s distinction (in his London Times article) between the two approaches. The distinction is glossed by Mattias Frisch as follows:

According to Einstein, we can distinguish constructive theories that treat phenomena as complex and build them up out of ‘‘the materials of a relatively simple formal scheme’’ from principle theories that rely on empirically discovered, general characteristics of natural processes. As it is usually understood, Einstein’s distinction is a distinction between theories that describe the directly observable macroscopic behavior of a system with the help of phenomenological principles, which are elevated to the status of postulates, and theories that describe a system’s behavior by proposing a model of its detailed microscopic constitution. This interpretation fits well with the examples Einstein gives of the two kinds of theories: the kinetic theory of gases, on one hand, which derives the behavior of gases from a microscopic model, and thermodynamics, on the other hand, which is based on phenomenological principles such as the principle that there can be no perpetual motion. (“Principle or Constructive Relativity,” SHPS-B, p. 178)

Here we can usefully note several oppositions. The microscopic (sub-sensible) and attendant mathematical-theoretical structure is opposed to the macroscopic (grossly sensible) and attendant postulates more proximate to common experience. This distinction does not track but rather echoes distinctions to be found in the ancient Aristotelian logic of science: between what is better known quoad nos (to us at first) as opposed to what is better known quoad se (in itself); between a demonstration that something is the case (demonstration of the fact, demonstratio quia) as opposed to demonstration why something is the case (causal demonstration, demonstratio propter quid). Above all, it echoes the Aristotelian marching orders at the beginning of the Physics: we must proceed from what is better known to us towards the principles, causes, and elements of things. However, what is better known to us is known in vague generalities, contexts close to home (and thus subject to inductive undersampling), and through names that track reality only meagerly at first. Yet, these first forays contain within them, in potency, all of what comes later; otherwise, true intellectual progress and discovery based upon what we know at first would be impossible, and we cannot but utilize what we know at first!

With such distinctions in mind, we might be able to see why Aristotle won out over Democritus for so long. Democritus himself desired the constructive theory, for he quipped: “We really know nothing. Truth is in the depth.” (DK 117; D. H. Berquist translation) That is, the senses grant us access to the phenomenologically immediate, what is present to us on the macroscopic level, shading into the mesoscopic. Democritus wanted to reach the deep underpinnings of things. Yet he realized, in the following fragment, that there were dangers in attempting truth “in the depth” while bypassing knowledge through the senses:

[The mind says:] Color is by custom, the sweet is by custom, the bitter is by custom but in truth, the atoms and the empty. [And he makes the senses reply to the mind:] Wretched mind, taking your beliefs [arguments] from us, you try to overthrow us. The overthrow will be your downfall. (Democritus, DK 125)

This is why it might surprise our chemistry professor (or yourself) to read the following praise lavished upon the Atomic Master by the Stagirite:

In general, no one except Democritus has applied himself to any of these matters in a more than superficial way. Democritus, however, does seem not only to have thought about all the problems, but also to be distinguished from the outset by his method. (Aristotle, On Generation & Corruption, I.2, 315a34–315b2)

Nonetheless, he qualifies shortly afterwards (including the student of the Atomic Master):

Democritus and Leucippus, however, postulate the ‘figures’ [of the atoms], and make alteration and coming-to-be result from them. They explain coming-to-be and passing-away by their dissociation and association, but alteration by their grouping and position. And since they thought that the truth lay in the appearance, and the appearances are conflicting and infinitely many, they made the ‘figures’ infinite in number. Hence—owing to the changes of the compound— the same thing seems different to different people: it is transposed by a small additional ingredient, and appears utterly other by the transposition of a single constituent. For Tragedy and Comedy are both composed of the same letters. (ibid., 315b7–14)

That is, Democritus utilized a hypothesis regarding the (infinitely variable) structural arrangement of the proposed ultimate atomic constituents to account for not only the objective variety in natural materials but also the subjective variety of the appearance of those materials (the same dress appears different colors to different people). Now, the reason Aristotle wishes to qualify this approach has to do with his own account of “coming-to-be” (or substantial change, the larger genus of what is now called chemical change). More on this anon.

• The Chymical Principles of Aristotle

We should now, however, attempt to begin the answer to our question regarding why Aristotelian chymical ideas were so gripping for so long.

Aristotle provides his derivation of the chymical elements (earth, air, fire, water), in On Generation and Corruption, Book II, Chapters 1–3. Chapter 1 frames the question in general; chapter 2 argues for the fundamental features of sensible reality from which Aristotle proposes to derive the existence of the elements; chapter 3 connects the elements (in both their merely apparent and truly elemental forms) with these sensible features so as to provide empirical confirmation for the theory. We can briefly review and then comment on these three steps.

In this latter stage of his treatise, Aristotle relies upon his defense of the reality of substantial change (generation and corruption simply speaking) as well as its distinction from alteration (generation and corruption qualifiedly speaking: alterations). In modern terms, Aristotle believes that he has sufficiently distinguished between chemical changes and physical changes, and now he wishes to establish the elemental constituents of chymical change. He does so by providing an array of distinctions that links what is perceptible about “physical changes” (alterations) with what is present at a more fundamental level (“chemical changes”).

Thus as principles we have firstly that which is potentially perceptible body, secondly the contrarieties (I mean, e.g., heat and cold), and thirdly Fire, Water, and the like. For these bodies change into one another (they are not immutable as Empedocles and other thinkers assert, since alteration would then have been impossible), whereas the contrarieties do not change. Nevertheless, even so the question remains: What sorts of contrarieties, and how many of them, are to be accounted principles of body? For all the other thinkers assume and use them without explaining why they are these or why they are just so many. (ibid., II.1, 329a32–329b5)

That is, we begin phenomenologically (at the level of a “principle theory,” as it were) with body that can be sensed by us (the macroscopic and mesoscopic) as well as the contraries that are also sensible (more on these in a moment). Lastly, we have the sensible and apparently (that is, appearing to us) differing-in-kind bodies: the four elements. Note the reason Aristotle gives explaining why these fundamental elements change into each other: otherwise alteration would have been impossible. That is, he is thinking that were the elements completely impervious to change, they would not afford any possibility of mutually affecting each other. But they do mutually affect each other (It is an item for further consideration that this essential tie between the substance of a thing and its action-reaction relationships with its surroundings possesses axiomatic status in natural science.) The unchanging aspects of the fundamental character of matter are the contrarieties themselves. Because they are opposed to each other essentially, they cannot change into each other (heat cannot become coldness, although something hot can become something cold; today we would say that positive charge cannot become negative charge, although an atom that is positive or neutral can become an atom that is negatively charged).

Thus, our central question regarding the fundamentals of matter—says Aristotle—must attempt to find something invariant about the qualities which permit substances to undergo change. These qualities are the contraries—and everyone says as much, says the Stagirite (and even today we have electronic qualities of atomic particles that have contrary properties!). So, which qualities are the most fundamental?

This is the second stage of the argument. This is where we hear the crucial step in Aristotle’s thinking and find out the reason why his ideas held thinkers in thrall for so long. Fundamentally, it is because his theory was eminently empirical.

Here begins his key line of reasoning:

Since, then, we are looking for principles of perceptible body; and since perceptible is equivalent to tangible, and tangible is that of which the perception is touch, it is clear that not all the contrarieties constitute forms and principles of body, but only those which correspond to touch. For it is in accordance with a contrariety—a contrariety, moreover, of tangible qualities—that the primary bodies are differentiated. (ibid., II.2, 329b5–11)

We are looking for the principles of bodies that we can perceive. This should strike one who recalls that the usual view is that Aristotelian physics is about changing and changeable beings, the physika onta, whether or not they are perceptible. Now, “perceptible body” could signify “corporeal body” only insofar as it is perceptible, or it could mean “corporeal body” that is also perceptible. The former makes perceptibility essential to the inquiry into chymical principles, the latter makes it accidental. What is more, it is not just any perceptible qualities that are needed, but the ones that correspond to touch. Yet in other places, Aristotle is clear in maintaining that not all physical beings need be perceptible and touchable. Perhaps, then, he does not mean perceptible body in the macroscopic sense, but that as we approach the mesoscopic level, we reach an identity between what is first in being and what is first to us. The chymical principles of things are fine-grained, but only qua what is the very root and origin of what is macroscopically sensible. That is, one might say, the chymical principles are those of “potentially sensible bodies” because they—if added up sufficiently—do compose the bodies readily able to be sensed. They are the fine-grains of things at the very bottom of actual, tangible, bodily reality.

If this is the case, then, we must look for the contraries that are the most fundamental. That is, if bodily beings are material composites, and their materials are most of all formed through the interaction of contrary qualities, then the most fundamental of these contrary qualities with provide us with the principles or elements of things. Aristotle does this in the following passage:

Accordingly, we must segregate the tangible differences and contrarieties, and distinguish which amongst them are primary. Contrarieties correlative to touch are the following: hot-cold, dry-moist, heavy-light, hard-soft, viscous-brittle, rough-smooth, coarse-fine. Of these heavy and light are neither active nor susceptible. Things are not called heavy and light because they act upon, or suffer action from, other things. But the elements must be reciprocally active and susceptible, since they combine and are transformed into one another. On the other hand, hot and cold, and dry and moist, are terms, of which the first pair implies power to act and the second pair susceptibility. . . .  From these are derived the fine and coarse, viscous and brittle, hard and soft, and the remaining differences. (ibid., 329b16–25, b33)

So, having argued that the chymical principles are at root identical to the principles of touchable objects, and these principles arrange themselves according to contrary qualities, we take a survey of these qualities. Of course, we must then ask if all of these qualities are equally fundamental. Aristotle answers no. He instead looks for qualities that allow most of all for change, and this is action and passion: “the elements must be reciprocally active and susceptible, since they combine and are transformed into one another.” It does not make sense to explain the readily transmutable and transmutations using inert principles. Consequently, heavy and light are eliminated. Besides, these pertain to a treatment of physical cosmology, in the De Caelo—how quaint: even in Aristotle’s time, the “gravitational” force was severed from the fundamental “chemical/elemental” forces. Furthermore, Aristotle uses the heavy and the light and their relationships with natural places the his geocentric cosmos to provide the global physical origins of his four elements, which are not their chemical origins. Yet even in today’s cosmology, the elements originate only in special places and times in the cosmos (Big Bang and stellar nucleosynthesis).

Among the others (hard-soft, viscous-brittle, rough-smooth, coarse-fine), Aristotle provides an array of arguments attempting to derive these qualities from the fundamental four (hot-cold, dry-moist). Indeed, note how these four align with rudimentary chymical features and even the phases of matter:

Hot is that which associates things of the same kind (for dissociating, which people attribute to Fire as its function, is associating things of the same class, since its effect is to eliminate what is foreign), while cold is that which brings together, i.e. associates, homogeneous and heterogeneous things alike. And moist is that which, being readily adaptable in shape, is not determinable by any limit of its own; while dry is that which is readily determinable by its own limit, but not readily adaptable in shape. (ibid., 329b26–32)

Here is my amateur attempt at some correlations. Note that the first pair are powers to act, and as such they are opposed to each other:

Hot: a power to act that associates the like (by purifying it of the unlike)—So, akin to repulsion; since it is associated with fire, it is akin to the plasma phase
Cold: a power to act that associates the unlike—So, akin to attraction; since it is a power to act, then it finds an unlikely counterpart in phases of matter near absolute zero

Note how this notion of “the hot” is still operative insofar as chemists use distillation and take advantage of the various boiling points of different substances in their practical work. Note now how the second pair are defined by opposed features of “adaptable in shape” and “determinable by a limit”. They each possess the opposite quality of these two features:

– Moist: a disposition to being acted upon, which is readily adaptable in shape but not by being determined by its own limit—So, akin to fluid states of matter (liquids and gases)
– Dry: a disposition to being acted upon, which is not readily adaptable in shape by being determined by its own limit—So, akin to solid states of matter

Note how concerned Aristotle is with explaining what is phenomenologically obvious about all of the bodies which have matter and experience material interactions. There must be fundamental active powers that govern these interactions. It is nice to image hot and cold as akin to interactions between positive and electric charges, or between high and low energy phases of matter. But more importantly they are ubiquitous contraries, so they have the requisite character of being present and active in all material things. The moist and dry correspond to all observed physical phases of matter insofar as matter can be shaped and have things done to it. So Aristotle concludes On Generation and Corruption, II.3: “It is clear, then, that all the other differences reduce to the first four, but that these admit of no further reduction. For the hot is not essentially moist or dry, nor the moist essentially hot or cold; nor are the cold and the dry derivative forms, either of one another or of the hot and the moist. Hence these must be four.”

Thus, Aristotle’s method latches on to principles that attempt to track all activity and reactivity of all chemical phases. His crucial error is identifying these principles with tangible qualities. Here is how De Koninck describes this error:

It is true that it is by a long detour that one arrives at this identification, but, at the end of the story, the identity is taken to be established: “calidum et frigidum, humidum et siccum, secundum quae distinguuntur quatuor elementa,” are indeed also the proper sensible objects of touch. The theory concludes to the coincidence between that which is most elementary in itself in material things and that which is most elementary for us in knowledge. And since, in fact, touch is par excellence the sense of certitude, the identification of what which is first in things from the point of view of matter, with that which is as well the most known by us, however hypothetical it may be, will be no less tenacious. It will become too reassuring to be placed in doubt. And so it has been maintained through many centuries. We understand that the principle of the primacy of experience in natural science, a principle on which Aristotle insists in the very treatise where he expounds the theory of the elements, has remained so long inoperative in this domain. (Charles De Koninck, “Introduction to the Study of the Soul”)

He then goes on to cite Aristotle’s rousing methodological statement, which should resonate with every experimentalist:

Lack of experience diminishes our power of taking a comprehensive view of the admitted facts. Hence those who dwell in intimate association with nature and its phenomena are more able to lay down principles such as to admit of a wide and coherent development; while those whom devotion to abstract discussions has rendered unobservant of the facts are too ready to dogmatize on the basis of a few observations. The rival treatments of the subject now before us will serve to illustrate how great is the difference between a scientific and a dialectical method of inquiry. For, whereas the one school argues that there must be atomic magnitudes because otherwise The Triangle will be more than one, Democritus would appear to have been convinced by arguments appropriate to the subject, i.e. drawn from the science of nature. (On Generation and Corruption, I.2, 316a5–15)

Aristotle closes his inquiry into the fundamental chymical principles by showing the allowed physical combinatorics of the four primary chymical qualities:

The elements are four, and any four terms can be combined in six couples. Contraries, however, refuse to be coupled; for it is impossible for the same thing to be hot and cold, or moist and dry. Hence it is evident that the couplings of the elements will be four: hot with dry and moist with hot, and again cold with dry and cold with moist. And these four couples have attached themselves to the apparently simple bodies (Fire, Air, Water, and Earth) in a manner consonant with theory. For Fire is hot and dry, whereas Air is hot and moist (Air being a sort of vapour); and Water is cold and moist, while Earth is cold and dry. Thus the differences are reasonably distributed among the primary bodies, and the number of the latter is consonant with theory. (ibid., II.3, 330a30–b8)

That is, since the contraries cannot be coupled with themselves or with their opposing contrary, we obtain only four possible combinations, which in turn—as qualitative powers and passivities in matter—lead from the sensible accidents to the essential natures of matter. Note how Aristotle says “the apparently simple bodies.” This is because he later (in the same chapter) distinguishes the apparently from the truly simple:

In fact, however, fire and air, and each of the bodies we have mentioned, are not simple, but combined. The simple bodies are indeed similar in nature to them, but not identical with them. Thus the simple body corresponding to fire is fire-like, not fire; that which corresponds to air is air-like; and so on with the rest of them. (ibid., 330b21–22)

That is, Aristotle is not asserting that we literally sense the chymical elements. Rather, our sense of touch leads us, through macroscopically and mesoscopically sensible and tangible qualities, to the fundamental forces of chymical natures. Their purest forms are always and ever present in coarser, impure manifestations, but our senses are sufficient to trace the tangled branches all the way to just near enough the root of things to possess chymical science. There is no “deep down things” that we could never hope to see and cannot even imagine. The thralldom of the senses really signifies that of the proper sensibles (colors, odors, the tangible, the audible, etc.); it is “broken” by including in our consideration the common sensibles (motion, quantities, numbers, shapes) as well as their patterns over time.

• The Non-Skeptical Chymist

More could be said. We should, however, note in closing that this connection to touch and the macro- and mesoscopic sense level is the reason why Aristotle reigned so long as king of chemistry. But before chymistry became chemistry, we had to determine a method to deny the senses without overthrowing them. This “path” towards chemical discovery is therefore not an easy one to find. One can contemplate this by surveying the timeline of the discoveries of the chemical elements. (Or, this feature of the interactive periodic table allows you to animate their discovery—most are post 1750.) That is, even the recognition of what elements are and their isolation—much less the discovery of their periodicity and hence deep interconnection—is far from the domain of our senses.

And this itself—the domain of our senses—is another key aspect to consider. Our domain (with livable temperatures and pressures) is a small area on typical phase diagrams of matter:

(source: Wikimedia commons)

Consider this for the commonly observed material known as water:

(source: this awesome website about water)

Note the circled “E” on the diagram. There lies the common temperatures and pressures we experience in our habitable environments, beyond which we cannot experience much in the body insofar as we would be dead. Thus, most of the nature of matter exists beyond realms where we can immediately experience through the sense of touch without damaging that faculty.

We could note other things (such as the real reason for Aristotle’s opposition to Democritean atomism not being the existence of minima naturalia as such—for this became a commonplace in medieval natural science—but rather the physical reductionism that this implies). Yet we have done enough to answer our question: Is there a good reason for why Aristotle’s approach was the dominant one for so long? The answer is yes: it is because of the thralldom of the senses in the mesoscopic phenomenology that initiates Aristotelian Chymistry, a thralldom that cannot be rebelled against too thoroughly without undermining the foundations of any regime that would replace it. The senses—and the sense of the living, understanding chemist—must be given a seat in government in the new order.

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