Reading Aristotle: Physics 1.8: Essential and Accidental Change

In Physics 1.7, Aristotle determined the “number and nature” of the principles of nature. In chapter eight, the penultimate chapter of book one, he discusses the “error” of previous thinkers in denying the reality of change.

“We will no proceed to show that the difficulty of the early thinkers, as well as our own, is solved in this way alone. The first of those who studied science were misled in their search for the truth and the nature of things by their inexperience, which as it were thrust them into another path. So they say that none of the things that are either comes to be or passes out of existence, because what comes to be must do so either from what is or from what is not, both of which are impossible. For what is cannot come to be (because it is already), and from what is not nothing could have come to be (because something must be present as a substratum). So too they exaggerated the consequence of this, and went so far as to deny even the existence of a plurality of things, maintaining that only Being itself is. Such then was their opinion, and such the reason for its adoption” (Physics 1.8, 191a23-33) [1]

I find the history of philosophical/intellectual development fascinating, almost as fascinating as the philosophical content on its own. The emergence of early Greek philosophy is quite unprecedented in history, and unsurpassable in its significance and influence. The early Greek philosophers were attempting to understand the natural world in which they found themselves, and they were doing so by searching for the “principles” of nature, the explanation of why things were/happened the way they did. This led some of them to adopt quite radical positions. Aristotle, throughout much of the Physics and the rest of his works, takes a sharp and definitive stand of disagreement against these prior philosophers, but here he at least admits a sympathetic understanding of how they went astray. They were, he suggests, “misled . . . by their inexperience”, which is not surprising, considering that they were literally the trail blazers of all western science and philosophy. But, whether or not their error is understandable or not, it still remains error, and it is to this that Aristotle offers his response.

In particular, he is responding here to the assertion that “none of the things that are either comes to be or passes out of existence”, which is most famously a view held by Parmenides. The ancients recognized that nature is a reality which appears to be constantly undergoing change, and processes of becoming, and growth, and corruption, and alteration and transition, etc. And this gave them an immense amount of metaphysical trouble, so much so that they were sometimes led to extreme positions, such as denying the existence of any real change whatsoever at all, or denying the existence of any real stability whatsoever at all, i.e. insisting that change is all that exists. Aristotle is examining the former here.

Parmenides wrote:

One road there is, signposted in this wise:

Being was never born and never dies.

Four-square, unmoved, no end it will allow.

It never was, nor will be; all is now,

One and continuous. How could it be born

Or whence could it be grown? Unbeing?—No—

That mayn’t be said or thought; we cannot go

So far ev’n to deny it is. What need,

Early or late, could Being from Unbeing seed?

Thus it must altogether be or not [2].

We’ve seen before that Parmenides thought that any real change would require something to come into existence from nothing, which he took to be strictly impossible. Aristotle, summarizing this line of thought, writes that Parmenides (and others) held this to be the case “because what comes to be must do so either from what is or from what is not, both of which are impossible. Why think that both of these options are impossible? For the first, “what is cannot come to be” because it already is. In other words, if something “comes to be”, that means it was not previously there. If something is there, it cannot then “come to be”. For the second, “from what is not nothing could have come to be”, because something cannot come from nothing, and, Aristotle adds, any change implies a pre-existing, underlying “substratum”, which he has discussed in previous chapters.

But, Aristotle insists, these earlier thinkers have “exaggerated” the consequences/implications of this reasoning. He notes that they “went so far as to deny the existence of a plurality of things, maintaining that only Being itself is” (a view which is known as “monism”), which he adamantly disagrees with. That there is  “plurality” and “change” in nature he takes as just exceedingly obvious and undeniable, perhaps even necessary in order to undertake any science of physics (as he suggests in 1.2).

So this is the problem. Now he goes about trying to offer a solution:

“Our explanation on the other hand is that the phrases ‘something comes to be from what is or from what is not’, ‘what is not or what is does something or has something done to it or becomes some particular thing’, are to be taken (in the first way of putting our explanation) in the same sense as ‘a doctor does something or has something done to him’, ‘is or becomes something from being a doctor’. These expressions may be taken in two senses, and so too, clearly, may ‘from being’, and ‘being acts or is acted on’. A doctor builds a house, not qua doctor, but qua housebuilder, and turns gray, not qua doctor, but qua dark-haired. On the other hand he doctors or fails to doctor qua doctorBut we are using words most appropriately when we say that a doctor does something or undergoes something, or becomes something from being a doctor, if he does, undergoes, or becomes qua doctor. Clearly then also ‘to come to be so-and-so from not-being’ means ‘qua not being'” (191a33-191b9) [3].

In our normal, everyday common sense understanding of the world, and in the way we ordinarily conceive of things and discuss them with others, we usually take it as a given that there are numerous different types of beings that are at least in some sense separate and distinct from others. Most obviously, we take it for granted that I am an “I”, an individual person who is in some way separate and distinct from you, and her, and them, and all other persons who consider themselves likewise to be a unique “I”. But we also think as such about other things as well. This tree and that zebra and this planet and that star. We talk about a thing as if it is “a being”, somehow different from “being” itself, as such; i.e. existence considered broadly. Parmenides, however, challenged this common sense thinking. For him, there is just one fundamental principle of everything, and that is “being” or “existence” in itself. And this must be completely and absolutely one. For how could anything be separate or distinct from “being” itself? If something is “other than” being, by definition it is non-being (so Parmenides would suggest). But if it is non-being, it does not exist; it’s nothing. So there can be nothing but the “oneness” of being, no separate “beings”, no distinction between this being and that being, just being itself. So when we say something such as “something comes to be from what is or from what is not”, a strict monist might insist that we can only interpret this in one, limited sense–that sense being what they would argue against, namely that being can come from either being or non-being, that any real change at all can occur. But here, Aristotle says that such an interpretation would in fact be a misunderstanding, because there can be two meanings of statements in that order.

As an example, he uses a doctor. In particular, he examines statements of a structure such as “a doctor does something or has something done to him” or “X is or becomes something from being a doctor”. These sentences, he suggests, may be taken in two senses. The first sense is what Aquinas calls “per accidens attribution” or “accidental attribution”. Such a statement might be: “a doctor builds a house”. This is a perfectly normal and sensible statement. After all, doctors are presumably capable of building things; there doesn’t seem to be any reason to deny that that is the case. But what Aristotle is getting at here is that, actually, doctors don’t build houses, at least not “qua doctor”, or not insofar as they are a doctor. Rather, doctors only build houses accidentally; they only do so insofar as they also happen to be housebuilders, or people capable of building houses. The idea here is that, when in a statement we refer to the subject in a particular way, we are, in a sense, identifying part of that subject’s form. When I say “a doctor built that house”, by referring to him, the subject, as “doctor”, I am calling attention to some specific fact about him, about who/what he is, what his form/nature is. The form of the particular person I’m referring to includes, in this case, “being a doctor”. But it also includes “being a housebuilder” or being able to build a house. If it did not include this, the person would, by definition, be incapable of producing a house. So the form of this person must include both “being a doctor” and “being a housebuilder”. But, we might ask, when this person actually goes about building a house, what part or aspect of their form is being actualized, doing the action? And the answer is that the “housebuilder” aspect of his form is what is carrying out the action. So when a doctor builds a house, it is not because he is a doctor, since it is not the “nature” of doctors to build houses, not part of the definition of what it is to be a doctor to build houses. Doctors certainly might be capable of building houses, but not for the reason that they are doctors. Being a doctor has nothing to do with their being able to build houses. Hence, being a doctor is only an “accidental” feature of building a house, not related essentially. (For a rather silly example to drive the point across: imagine a man goes in to see a doctor because he’s been having some back pain. The doctor asks “why’d you come in?” and the man responds “I have brown hair”. Now, it may be certainly true that the man does indeed have brown hair, but this is hardly relevant to the reason why he’s come in to see the doctor. It is an inessential fact, an “accidental” feature that cannot be considered as an adequate cause/reason for the action in question. In the same way, that a man who builds a house happens to be a doctor is inessential to his action of building the house, since any number of people who are not doctors could also build a house, and there might perhaps be some doctors incapable of doing such).

The second sense is “per se attribution”, or essential attribution. In this case, the statement might be something like “a doctor heals, or performs surgery, or applies a bandage”. In this case, the action that the subject performs is performed qua his being a doctor. It is part of the nature/function of a doctor to carry out these actions, so, when the man does them, he is doing them insofar as he is a doctor. Now, Aristotle points out that “we are using words most appropriately when” we use them in this second, essential sense. For it more accurately and meaningfully conveys a correct statement when we say that a housebuilder builds a house, rather than that a doctor does so. The latter is not wrong, it just not as “correct” as the former.

His point in all this is that, just as statements about actions as such can have two senses, so can statements about being and change. Just as saying “a doctor does something or has something done to him” can either imply an accidental or essential attribution, so also can saying “something comes to be from what is or from what is not” or “what is not or what is does something or has something done to it or becomes some particular thing”. Just as, in its most appropriate usage, attributing something to a doctor implies that it is such qua doctor, so saying “to come to be so-and-so from not-being” means that so-and-so comes to be qua not being, or insofar as it previously was not-being.

He continues:

“It was through failure to make this distinction that those thinkers gave the matter up, and through this error that they went so much farther astray as to suppose that nothing else comes to be or exists apart from Being itself, thus doing away with all becoming” (191b10-13) [4].

So, he says, the reason the prior thinkers fell into their error of denying any real change or multiplicity is because they failed to recognize this distinction, between accidental and essential attribution. How so?

“We ourselves are in agreement with them in holding that nothing can be said without qualification to come from what is not. But nevertheless we maintain that a thing may ‘come to be from what is not’–that is, in a qualified sense. For a thing comes to be from the privation, which in its own nature is not-being–this not surviving as a constituent of the result. Yet this causes surprise, and it is thought impossible that something should come to be in the way described from what is not” (191b13-18) [5].

Here, Aristotle actually admits that the ancients were correct, at least in one of the two senses. For it is true that something cannot come from nothing, per se. But per accidens, something might theoretically be able to come from nothing? This is, after all, what happens when something comes to be from a “privation”. Remember from previous chapters that when something comes to be, it comes to be from its previous absence/contrary. So when a stove becomes hot, it does so from having previously been not-hot. When a fire is lit, the fire becomes from there previously having been no fire. This is a “privation”, a lack or absence of something, from which that thing comes to be. But a privation, “in its own nature”, just is not-being, at least in a sense. For a privation does not have any real, positive, actual existence. To say that something is “not on fire” is to say something about what it is not, not about what it is. Any number of things could be “not on fire”–a giraffe, a television, an ocean. A privation merely notes an absence or lack of some positive thing; so in that sense, a privation is a “non-being” of that thing, its non-existence in a particular way/aspect/time/place. And since Aristotle believes that things really do come into existence from privations (i.e. go from being not on fire to being on fire, or go from being young to being old), he therefore really does believe that, “in a qualified sense”, things really do come into being from non-being. But this is only per accidens. The fact that a particular log is currently not on fire does not positively contribute to its at some point catching fire, just as the fact that a particular man is a doctor does not positively contribute to his at some point building a house. The privation, Aristotle notes, does “not [survive] as a constituent of the result”. In other words, when a thing comes to be, the privation, necessarily, ceases to be. A log cannot both be “on fire” and “not on fire” at the exact same time. Precisely as soon as the log catches on fire, the privation ceases to be. “Not being on fire”, as we’ve said, does not contribute positively, or causally, to there coming to be a fire on some log. Rather, what does contribute is, perhaps, a match, or a torch, or a lighter, etc. These things account for the log catching on fire per se, just as a housebuilder accounts for the building of a house per se. In a per se sense, it is of course true that being could not come from non-being. If there were, for instance, absolutely nothing, then nothing would ever come to exist. But just because a thing is lacking some positive feature, some “being”, and then comes to have it from having not had it, does not imply that being has come into being from nothing.

He goes on:

“In the same way we maintain that nothing comes to be from being, and that being does not come to be except in a qualified sense. In that way, however, it does, just as animal might come to be from animal, and an animal of a certain kind from an animal of a certain kind. Thus, suppose a dog to come to be from a horse. The dog would then, it is true, come to be from animal (as well as from an animal of a certain kind) but not as animal, for that is already there. But if anything is to become an animal, not in a qualified sense, it will not be from animal: and if being, not from being–nor from not-being either, for it has been explained that by ‘from not-being’ we mean from not being qua not-being” (191b1827) [6].

Likewise, he also agrees that being cannot come from being, per se, but only in a qualified sense. Since this is not a usual way we think about things today, it may be useful to provide an illustration: suppose I draw a triangle on a sheet of paper. Then, after some time, I tell you that I am going to change the triangle. I take the paper, and when I give it back, you look but can see no discernible difference. The triangle is exactly the same now as it was before. If the triangle really is exactly the same now as it was before, then we could hardly say that it has “changed” in any way. Similarly, if I say that a man has changed and become a doctor, from previously having been a doctor, this would be nonsensical. If he already was a doctor, and is still a doctor now, it doesn’t make sense to say that he’s “changed” at least in relation to his status as a doctor. If I say that an animal has changed, and gone from being an animal, to being an animal, the same result is reached; there just is no “change” to speak of. So, Parmenides and some of the other ancients would say, this means that since being is what is, and there is nothing “outside” or “other than” being that being could possible become (since anything outside or other than being is by definition nothing), then there is nothing for being to change into, and hence being cannot change. Being cannot “come from” being, since being already is being.

And Aristotle agrees. Being cannot come from being. Per se. Being can, however, come from being per accidens. So, imagine (again using a silly example, to get the point across) that a dog comes to be from a horse. Obviously physically impossible, but just suppose. (Note: this is not just saying that a horse reproduces and gives birth to a dog, it is rather saying that a horse itself actually becomes a dog). Now, if a horse suddenly transformed into a dog before our eyes, we’d very much want to say that some sort of change has occurred. But what if someone standing next to us, who also saw the peculiar event unfold, denies that it was a real change. Astounded, you ask him why, and he says, “Well, it was an animal before, and it’s still an animal now. It went from being an animal, to being an animal, so no change real change occurred!” But this, Aristotle says, just totally mistakes what is taking place. The horse becomes a dog, not insofar as it was an animal, but rather insofar as it was a horse. It is correct that the dog has not changed from being an animal, but it is correct that, insofar as it was once a horse and is now a dog, it has indeed changed. On the other hand, if something “becomes” an animal in an unqualified sense, it cannot have done so from previously having been an animal. A horse that turns into a dog does not “become” an animal per se, even though it is an animal. But a table that becomes a dog does become an animal per se, since it “becomes” an animal insofar as it previously was not an animal.

And so, Aristotle says, the same is true in consideration of “being”. If, for example, a seed becomes an oak tree, it is correct in a sense to say that it was a being before, and a being after, so it is always being and therefore, in that respect, does not change. But it is incorrect to thus conclude that absolutely no change has taken place. For a seed does not change into an oak tree insofar as it was a being, but rather insofar as it was a seed.

“Note further that we do not subvert the principle that everything either is or is not. This then is one way of solving the difficulty. Another consists in pointing out that the same things can be explained in terms of potentiality and actuality. But this has been done with greater precision elsewhere” (191b27-29) [7].

First, he says he does not deny “the principle that everything either is or is not”, the principle which some of the earlier thinkers had taken to mean that change cannot occur. Second, he concludes that what he has just said is enough to answer the problem of the monists. But, he adds, one could (and should) also answer the problem by way of reference to his famous “act/potency” principles. But this he has done elsewhere (which we will look at in due course).

He finishes:

“So as we said, the difficulties which constrain people to deny the existence of some of the things we mentioned are now solved. For it was this reasoning which also caused some of the earlier thinkers to turn so far aside from the road which leads to coming to be and passing away and changing generally. If they had come in sight of this nature, all their ignorance would have been dispelled” (191b30-34) [8].

We will next turn to the ninth and final chapter of book one of the Physics.



[1]. McKeon, Richard, editor. The Basic Works of Aristotle. New York: Random House, Inc, 1941. Print, 233.

[2]. Parmenides DK 28 B8. 1-11. Quoted in Kenny, Anthony. A New History Of Western Philosophy. Oxford: OUP Oxford, 2010. eBook Academic Collection (EBSCOhost). Web. 24 Dec. 2016.

[3]. McKeon. Aristotle. 233.

[4]. Ibid. 233-234.

[5]. Ibid. 234.

[6]. Ibid.

[7]. Ibid.

[8]. Ibid.

Header image in the Public Domain in the United States, taken from Wikimedia Commons:


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