Reading Aristotle: Physics 1.2: Is Nature One or Many?

In my last post in this series, we read through Aristotle’s Physics Book 1, section 1, which discusses what “scientific knowledge” is, and how gaining this knowledge consists of starting from the obvious, general facts and digging deeper into their explanations, causes, principles, and elements.

We will now turn to section 2:

“The principles in question must be either (a) one or (b) more than one” (Physics 1.2, 184b15-16) [1].

When we seek knowledge, we are seeking the deepest, most fundamental principles/explanations able to be found. Here specifically we are seeking these principles as they pertain to nature. Obviously, the principle of nature must be either one or many.

“If (a) one, it must be either (i) motionless, as Parmenides and Melissus assert, or (ii) in motion, as the physicists hold, some declaring air to be the first principle, others water. If (b) more than one, then either (i) a finite or (ii) an infinite plurality. If (i) finite (but more than one), then either two or three or four or some other number. If (ii) infinite, then either as Democritus believed one in kind, but differing in shape or form; or different in kind and even contrary” (Physics 1.2, 184b17-23) [2].

Here Aristotle presents us with a thorough layout of the possible options. First he asks whether the first principle is one or many. If one, it might be something like the “theory of everything” which modern physicists search for (see my post on this here). If many, it might just be all the most fundamental particles and forces, such as quarks. If the former, the next question becomes whether or not it is in motion. This might seem a strange question for us today. In fact, it is an issue which contemporary physicists still discuss, but for now we’ll just focus on the context in which Aristotle was writing. He mentions two people who assert that the principle of nature is motionless: Parmenides and Melissus. Parmenides and Melissus were both presocratic philosophers of the “Eleatic School.” Relevant to Aristotle’s statement here, both philosophers held that all of reality is one and unchanging, and thus that “change, motion, and multiplicity are illusions” [3]. One writer says about Parmenides:

“Parmenides of Elea was a Presocratic Greek philosopher. As the first philosopher to inquire into the nature of existence itself, he is incontrovertibly credited as the “Father of Metaphysics.” As the first to employ deductive, a priori arguments to justify his claims, he competes with Aristotle for the title “Father of Logic.” He is also commonly thought of as the founder of the “Eleatic School” of thought—a philosophical label ascribed to Presocratics who purportedly argued that reality is in some sense a unified and unchanging singular entity. This has often been understood to mean there is just one thing in all of existence. In light of this questionable interpretation, Parmenides has traditionally been viewed as a pivotal figure in the history of philosophy: one who challenged the physical systems of his predecessors and set forth for his successors the metaphysical criteria any successful system must meet” [4].

On the other end of the spectrum are those who held that the principle of nature is in motion, the extreme end of which can be seen in the philosophy of Heraclitus. Ed Feser writes:

“For Heraclitus, permanence is an illusion, and change is the universal feature of reality” [5].

Of course, to say that everything is change raises an obvious problem: if everything is change and there is no stability or permanence, then a person giving an argument will not be the same person throughout the argument, the argument itself will change and will not be the same argument, and the standards of logic/reasoning employed will likewise have changed throughout the course of presenting the argument; all this rendering the position self-defeating [6]. This led Heraclitus to propose that opposite propositions can be true, thus rendering the “self-defeating” objection meaningless. Says one writer, Heraclitus “is best known for his doctrines that things are constantly changing (universal flux), that opposites coincide (unity of opposites), and that fire is the basic material of the world” [7].

The next options Aristotle gives are obvious, and logically exhaustive. If the principle of nature is more than one, then it will either by a finite (two, seven, three hundred, 42 million, etc) or an infinite multiplicity, meaning it would have no limit. Aristotle then refers to Democritus, who was another presocratic philosopher and the famous advocate of the “theory of atoms.” Here is a description of that theory:

To account for the world’s changing physical phenomena, Democritus asserted that space, or the Void, had an equal right with reality, or Being, to be considered existent. He conceived of the Void as a vacuum, an infinite space in which moved an infinite number of atoms that made up Being (i.e., the physical world). These atoms are eternal and invisible; absolutely small, so small that their size cannot be diminished (hence the name atomon, or “indivisible”); absolutely full and incompressible, as they are without pores and entirely fill the space they occupy; and homogeneous, differing only in shape, arrangement, position, and magnitude. But, while atoms thus differ in quantity, differences of quality are only apparent, owing to the impressions caused on the senses by different configurations and combinations of atoms. A thing is hot or cold, sweet or bitter, or hard or soft only by convention; the only things that exist in reality are atoms and the Void” [8].

The difference in quantity or “shape, arrangement, position, and magnitude” but not quality is what Aristotle is referring to when he says “as Democritus believed one in kind, but differing in shape or form”. For Democritus, there is an infinite number of atoms, and that, along with the Void, is what reality is; it is the principle of nature. The other logical possibility is for a principle of nature that is infinite in multiplicity but not alike in kind. We could imagine instead an infinite number of atoms, where each individual atom was an altogether unique, different kind of being.

(Notice that Aristotle doesn’t ask, if there are multiple principles, whether they are in motion or motionless. For, in his thought, a multiplicity would imply motion).

Aristotle says next:

“A similar inquiry is made by those who inquire into the number of existents: for they inquire whether the ultimate constituents of existing things are one or many, and if many, whether a finite or an infinite plurality. So they too are inquiring whether the principle or element is one or many. 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. For if Being is just one, and one in the way mentioned, there is a principle no longer, since a principle must be the principle of some thing or things” (Physics 1.2, 184b25-185a4) [9].

The “existents” here are just objects or beings which exist. Where the “principles” discussed above are the underlying explanations or causes of things, the existents are the actual things themselves. But the question is the exact same: is there just one being that exists or many? If many, is it a finite or infinite number? And in inquiring about this we are ultimately led back to the same place, for in seeking to understand the existents we must understand their principles.

Then Aristotle makes an interesting comment about the nature of science and philosophy. In my post Aristotle’s Answer to the Science/Philosophy Debate, I explained how Aristotle makes a distinction between “first” and “second” philosophy. Second philosophy can generally be understood as physics, while first philosophy might be considered “metaphysics.” Here’s one explanation:

“These causes and principles are clearly the subject matter of what he calls ‘first philosophy’. But this does not mean the branch of philosophy that should be studied first. Rather, it concerns issues that are in some sense the most fundamental or at the highest level of generality. Aristotle distinguished between things that are “better known to us” and things that are “better known in themselves,”[1] and maintained that we should begin our study of a given topic with things better known to us and arrive ultimately at an understanding of things better known in themselves. The principles studied by ‘first philosophy’ may seem very general and abstract, but they are, according to Aristotle, better known in themselves, however remote they may seem from the world of ordinary experience. Still, since they are to be studied only by one who has already studied nature (which is the subject matter of the Physics), they are quite appropriately described as coming “after the Physics” [10].

So why does Aristotle insist that “to investigate whether Being is one and motionless is not a contribution to the science of Nature”, i.e, to physics or second philosophy? Well, suppose you are a modern astronomer attempting to give a lecture on the redshift light of stars, when someone in the audience interrupts and objects that he doesn’t believe stars move at all. You could then respond with a plethora of data to explain why stars do in fact move and thus give off redshift, but suppose then the man says he doesn’t believe the scientific method or the process of science works at all. What then could you possibly say to him? Suppose he goes even farther and denies the validity of logic/reasoning; there is now no actual discussion to be had. Now obviously this is a very extreme example, but it illustrates the point Aristotle is making. If someone denies the very principles of geometry, a geometer “has nothing more to say” to him. In the same way, if the principles of nature are denied, then one who studies those principles can have nothing else to say in response. Remember that “principles” are underlying causes/explanations of things. But if there is just one thing that exists, and it is unchanging, how could it have an underlying cause? For the underlying cause would be something outside of itself, and thus there would in fact be more than one being which exists. So if being is one, then there are no principles; and if there are no principles, then the science of nature, whose very object is to uncover these principles, cannot even get underway. The science of nature, or “second philosophy”, just takes as its starting point that there are principles of nature; so it itself cannot respond to those who deny principles. Rather that task falls instead to first philosophy, or metaphysics. That is why Aristotle says “For if Being is just one, and one in the way mentioned, there is a principle no longer, since a principle must be the principle of some thing or things.” Note however that this is not to answer the question of whether the principle itself is one; just if being is one. There could still be multiple principles which apply to existents; but if there there is just one motionless being then there cannot be any principles.

Next Aristotle takes a little jab at some presocratic philosophers:

“To inquire therefore whether Being is one in this sense would be like arguing against any other position maintained for the sake of argument (such as the Heraclitean thesis, or such a thesis as that Being is one man) or like refuting a merely contentious argument — a description which applies to the arguments both of Melissus and of Parmenides: their premises are false and their conclusions do not follow. Or rather the argument of Melissus is gross and palpable and offers no difficulty at all: accept one ridiculous proposition and the rest follows — a simple enough proceeding” (Physics 1.2, 185a5-12) [11].

He then continues:

“We physicists, on the other hand, 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. Moreover, 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. At the same time the holders of the theory of which we are speaking do incidentally raise physical questions, though Nature is not their subject: so it will perhaps bee as well to spend a few words on them, especially as the inquiry is not without scientific interest” (Physics 1.2, 185a13-19) [12].

Basically, Aristotle is saying “I would be justified not giving an answer, because the question goes beyond the range of my object of study here; but since it is in some ways related, I’ll answer anyways.” Physicists must take for granted that there are multiple existents that are in motion, for the reasons looked at above. Indeed, a few books later, Aristotle gives this definition to nature itself:

“Nature has been defined as a ‘principle of motion and change’, and it is the subject of our inquiry” (Physics 3.1, 200b12) [13].

If there is no motion there can then be no physics, as Aristotle understands it. So how does he answer this question?

“The most pertinent question with which to begin will be this: In what sense is it asserted that all things are one? For ‘is’ is used in many senses. Do they mean that all things ‘are’ substance or quantities or qualities? And, further, are all things one substance — one man, one horse, or one soul — or quality and that one and the same — white or hot or something of the kind? These are all very different doctrines and all impossible to maintain” (Physics 1.2, 185a20-26) [14].

To understand this point completely might require a broader knowledge of Aristotelian philosophy. For now we’ll just explain that Aristotle is asking what type of being would exist, if being were just one: substance, quality, or quantity. These are three of Aristotle’s ten “categories” of being, which are discussed in depth in his book Categories. There is so much to say about these categories which must be left to a future post, so for now we’ll just give an extremely simplistic account. Substance refers to what a thing is; quality refers to how it is, its attributes/properties; and quantity refers to what degree it is, how much or what size, etc.

So, in response to those who say that “being is one,” Aristotle is asking, in what sense is being one? Is it one substance? Is it one in quality? One in quantity? If we cannot answer this question, then to say that “being is one” is so vague as to be almost meaningless. Even if we establish that being is one in substance, this raises the question: “And, further, are all things one substance”? He gives an example of different substances: a man or a horse. If we say that all being is one, and one in substance, and that substance is a horse, we could be saying either that all things that exist are horses, or that all things that exist altogether are one horse.

The Philosopher continues:

“For if both substance and quantity and quality are, then, whether these exist independently of each other or not, Being will be many” (Physics 1.2, 185a26-27) [15].

As we shall see next, Aristotle does not think that quality and quantity can exist on their own, independently of substance. But he still holds that quality and quantity are aspects of being; they are being in a sense. Parminedes’s whole argument against motion and multiplicity is that change would require being to come from non being (if a pot of water is cool, then there is no hotness in it. But if it boils and thus changes to become hot, that would require “hotness” to come from nothing). Aristotle argues that the act/potency distinction solves this problem (as we will discuss more in future posts), and thus he equates act with being. But if act is being, and if quality and quantity can be “acts” or actualities of substance, then this suggests a multiplicity in being.

“If on the other hand it is asserted that all things are quality or quantity, then, whether substance exists or not, an absurdity results, if indeed the impossible can properly be called absurd. For none of the others can exist independently: substance alone is independent: for everything is predicated of substance as subject. Now Melissus says that Being is infinite. It is then a quantity. For the infinite is in the category of quantity, whereas substance or quality or affection cannot be infinite except through a concomitant attribute, that is, if at the same time they are also quantities. For to define the infinite you must use quantity in your formula, but not substance or quality. If then Being is both substance and quantity, it is two, not one: if only substance, it is not infinite and has no magnitude; for to have that it will have to be a quantity” (Physics 1.2, 185a28-185b4) [16].

When Aristotle says “none of the others can exist independently: substance alone is independent: for everything is predicated of substance as subject” he means this: “green” and “four” are each examples of quality and quantity, respectively. But neither of these things can exist on their own. “Green” is a specific attribute which objects can have, but it as itself does not exist, independent of some object which contains it. You can have green apples, green paint, or green grass, but “greenness” on its own just doesn’t exist. In the same way, we often talk of/use numbers such as four, and sometimes we seem to do so without reference to substances. We might discuss a particular equation or math problem where the numbers are used independently of any objects; but this is just an abstraction — “numbers” on their own are abstract objects. In actuality, we would ask four what? These are all things that are predicated of subjects, but which without those subjects could not exist independently.

Similarly, if one were to assert that “being is infinite,” we would ask: “infinite what?” What is it that exists infinitely, or which exists in an infinite amount? Because “infinite” on its own is just a predicate of something, of some substance. This is why Aristotle says that an absurdity results. Because if all being were just a quantity or quality such as “infinite”, then in reality nothing would actually exist. In saying that “substance or quality or affection cannot be infinite except through a concomitant attribute, that is, if at the same time they are also quantities” he means that substances are not themselves quantities (“infinite” is not a substance), but that substances can have quantities and qualities as aspects or attributes of their being. Thus if substance exists with quantity or quality, then there will be a multiplicity of being; but if substance alone exists, it will not have quantity or quality. We would not be able to say that being is blue, or wide, or hot, etc (this is actually an extremely interesting point which I think might fit into some Thomistic theology, but that’ll have to wait for a later time).

Next Aristotle looks more at what we mean by “one.”

“Again, ‘one’ itself, no less than ‘being’, is used in many senses, so we must consider in what sense the word is used when it is said that the All is one. Now we say that (a) the continuous is one or that (b) the indivisible is one, or (c) things are said to be ‘one’, when their essence is one and the same, as ‘liquor’ and ‘drink’. If (a) their One is one in the sense of continuous, it is many, for the continuous is divisible ad infinitum. There is, indeed, a difficulty about part and whole, perhaps not relevant to the present argument, yet deserving consideration on its own account — namely, whether the part and the whole are one or more than one, and how they can be one or many, and, if they are more than one, in what sense they are more than one. (Similarly with the parts of wholes which are not continuous.) Further, if each of the two parts is indivisibly one with the whole, the difficulty arises that they will be indivisibly one with each other also” (Physics 1.2, 185b5-16) [17].

This section starts out listing the different ways in which something might be said to be “one” and then discusses the first option, that of a continuous being. Aristotle says that a continuous being is not actually one, because it is divisible into many. This then raises the question of “the one and the many.” If we have an object such as a car, we say that it is “one” car. But the car itself is a whole made up of many individual parts. If we take the car apart, even if we say the car itself is “one”, we will be left with “many”. This is a question for essentialism broadly, related in some ways to the famous “ship of Theseus” paradox.

For an example of something continuous, we can imagine if time were infinite, then it would stretch backward and forward forever. Thus time itself would be one continuous line. But we could divide this into many parts/sections: the “one” continuous line is actually made up of many successive centuries, decades, years, months, weeks, days, hours, minutes, seconds, etc. This the line of time is actually many, not one, or at least it can be divided as such. But what about things which cannot?

“But to proceed: If (b) their One is one as indivisible, nothing will have quantity or quality, and so the one will not be infinite, as Melissus says — nor, indeed, limited, as Parmenides says, for though the limit is indivisible, the limited is not” (Physics 1.2, 185b17-18) [18].

If something is indivisible it cannot have quantity or quality, because quantity and quantity are, in a way, “parts” of a being, and something indivisible cannot have parts. But to say that something is either infinite or limited is to assign to it quantity (admittedly, this does not entirely necessitate that being is not one, just that being is not one as Parmenides and Melissus argue, who are the most significant advocates of that position at the time). Which brings us to the last option:

“But if (c) all things are one in the sense of having the same definition, like ‘raiment’ and ‘dress’, then it turns out that they are maintaining the Heraclitean doctrine, for it will be the same thing ‘to be good’ and ‘to be bad’, and ‘to be good’ and ‘to be not good’, and so the same thing will be ‘good’ and ‘not good’, and man and horse; in fact, their view will be, not that all things are one, but that they are nothing; and that ‘to be of such-and-such a quality’ is the same as ‘to be of such-and-such a size” (Physics 1.2, 185b19-24) [19].

Here Aristotle examines the possibility of all things being one in the sense of having the same essence–similar to how we might say that all of humanity is one, because each individual human being shares the common essence of humanity. But this too results in absurdity, as Heraclitus held, that contradictory things can coincide. So if all things share the same essence, then a “man” and a “horse” are actually the same; or something that is “good” and something that is “not good” are one and the same; or something that is “true” and something that is “false” are the same. Aristotle goes even farther than calling this an absurdity: he says that the result is that they are actually nothing! For if good and not good are one and the same, then they are in effect meaningless. If this were true, we would be able to compare “yellow” and “seven” and say not just that they are analogically related, but that they are actually one and the same thing. So this cannot be the case.

He concludes this chapter like this:

“Even the more recent of the ancient thinkers were in a pother lest the same thing should turn out in their hands both one and many. So some, like Lycophron, were led to omit ‘is’, others to change the mode of expression and say ‘the man has been whitened’ instead of ‘is white’, and ‘walks’ instead of ‘is walking’, for fear that if they added the word ‘is’ they should be making the one to be many — as if ‘one’ and ‘being’ were always used in one and the same sense. What ‘is’ may be many either in definition (for example ‘to be white’ is one thing, ‘to be musical’ another, yet the same thing may be both, so the one is many) or by division, as the whole and its parts. On this point, indeed, they were already getting into difficulties and admitted that the one was many — as if there was any difficulty about the same thing being both one and many, provided that these are not opposites; for ‘one’ may mean either ‘potentially one’ or ‘actually one'” (Physics 1.2, 185b25-186a3) [20].

Aristotle here is showing how this problem, of “the one and the many” had so troubled and confused philosophers. In fact, his description of the problems some of these philosophers faced, and the giant hoops they jumped to get around them, makes them sound very similar to some modern/contemporary philosophers. Here is St. Thomas Aquinas’s discussion of this passage in his commentary on Aristotle’s Physics:

“Parmenides and Melissus erred because they did not know how to distinguish the uses of the term ‘one’. Thus, what is one in a certain respect, they said was one simply. But the later philosophers, also not knowing how to distinguish the uses of the term ‘one’, thought it absurd that one and the same thing should be in some way one and many. Yet, being convinced by the arguments, they were forced to believe it. And so Aristotle says that the later philosophers were ‘disturbed’ (that is, fell into a difficulty similar to that of the ancients, i.e., Parmenides and Melissus) lest they be forced to say that one and the same thing is one and many. Now this seemed absurd to both groups of philosophers. So the earlier philosophers, holding that all is one, rejected all multiplicity. The later philosophers, on the other hand, tried to remove multiplicity from anything they held to be one” [21].

The whole trouble, say Aristotle and Aquinas, is that these philosophers didn’t know how to distinguish the different senses/uses of the words “one.” So they were afraid to say “the man is white” because to say so would be to add quality to substance, resulting in multiplicity. But they didn’t realize that one could mean either one in essence, or one as a whole with parts. So Aristotle says that it is not necessarily an absurdity for the one to be many, and the many to be one, as long as the they are not contradictory (such as saying that “good” and “not good” are one).

Aristotle ends by introducing, or at least hinting at, his extremely significant theory of act/potency distinction as a possible solution to the problem of the one and the many. To fully flesh out this theory will be the object of a future post. To see briefly how it relates here, however, we will look at a quick example. A car is actually one, as a whole; but it is potentially many, if it is divided into its parts. Still, this is not to say that Aristotle thinks being is one; that is, in fact, the whole point of the chapter. Aristotle has examined the ways in which various philosophers assert that being is one, and shown them to be either absurd, or actually not one. For even if something is one actually but many potentially, the act/potency distinction itself implies multiplicity to an extent.

And so he will begin the next chapter, which we will examine in full in the next post in the series, by saying:

“If, then, we approach the thesis in this way it seems impossible for all things to be one” (Physics 1.3, 186a4-5) [22].


[1]. McKeon, Richard, editor. The Basic Works of Aristotle. New York: Random House, Inc, 1941. Print, Physics 1.2, 184b15-16. 

[2]. Ibid., Physics 1.2, 184b17-23.

[3]. Turner, William. “Melissus of Samos.” The Catholic Encyclopedia. Vol. 10. New York: Robert Appleton Company,1911. 22 Sept. 2016 <;.

[4]. DeLong, Jeremy C. “Parmenides of Elea (Late 6th cn.—Mid 5th cn. B.C.E.).” Internet Encyclopedia of Philosophy. Web. 22 Sept. 2016. <;.

[5]. Feser, Edward. The Last Superstition: A Refutation of the New Atheism. South Bend: St. Augustine’s Press, 2008. ebook.

[6]. See Feser, Edward. Scholastic Metaphysics: A Contemporary Introduction. Piscataway: Editiones Scholasticae/Transaction Books, 2014. Print, 33.

[7]. Graham, Daniel W., “Heraclitus”, The Stanford Encyclopedia of Philosophy (Fall 2015 Edition), Edward N. Zalta (ed.), URL = <;.

[8]. “Democritus”. Encyclopædia Britannica. Encyclopædia Britannica Online.
Encyclopædia Britannica Inc., 2016. Web. 23 Sep. 2016

[9]. McKeon, Richard, editor. The Basic Works of Aristotle. New York: Random House, Inc, 1941. Print, Physics 1.2, 184b25-185a4.

[10]. Cohen, S. Marc, “Aristotle’s Metaphysics”, The Stanford Encyclopedia of Philosophy (Summer 2016 Edition), Edward N. Zalta (ed.), URL = <;.

[11].  McKeon, Richard, editor. The Basic Works of Aristotle. New York: Random House, Inc, 1941. Print, Physics 1.2, 185a5-12.

[12]. Ibid., Physics 1.2, 185a13-19.

[13]. Ibid., Physics 3.1, 200b12.

[14]. Ibid., Physics 1.2, 185a20-26.

[15]. Ibid., Physics 1.2, 185a26-27.

[16]. Ibid., Physics 1.2, 185a28-185b4.

[17]. Ibid., Physics 1.2, 185b5-16.

[18]. Ibid., Physics 1.2, 185b17-18.

[19]. Ibid., Physics 1.2, 185b19-24.

[20]. Ibid., Physics 1.2, 185b25-186a3.

[21]. Thomas Aquinas. Commentary on Aristotle’s Physics. Books I-II translated by
Richard J. Blackwell, Richard J. Spath & W. Edmund Thirlkel
Yale U.P., 1963. <;.

[22]. McKeon, Richard, editor. The Basic Works of Aristotle. New York: Random House, Inc, 1941. Print, Physics 1.3, 186a4-5.

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