Potentiality and Possibility

“At the conclusion of Theta 3, we had recognized in dunamis at the same time the condition of becoming and a mode of being, and in energeia the mode of being that is opposed to it and which characterizes, beyond movement, all that which is effective. In defining what is in-potentiality as that which is not in-act, we have also distinguished it from non-being, in characterizing it as that which can be in act. Now we need to pursue the examination of what is in play in this division, or the modality of the relation of the in-potentiality to act” (Aubry, Dieu san la puissance, 2nd ed., ch. 4, p. 124, my translation throughout, with Becker number citations to Aristotle’s Greek text elided).

“The discussion of Theta 4 concerns neither dunamis nor what is dunamei, but rather the dunaton. This term nonetheless can designate both the possible and that which has power, or the capable, just as much as adunaton can designate the impossible as well as that which lacks power. In Theta 3, the dunaton had been defined in terms of dunamis as ‘that for which nothing makes it impossible for the act (energeia) to exist, when it is said to have power (dynamis)'” (ibid).

Clearly, dynamis, dynamei, and dynaton all have related etymologies. My Greek isn’t strong enough to just casually read Aristotle’s original the way I can mostly read Aubry’s French without a dictionary, so this is a bit of an eye-opener. This is why Aristotle’s discussions of what we render by English words that have different etymologies are so closely related.

Because the English words do not have this visible relation to one another, it is easy to be confused by the ways in which Aristotle relates the corresponding Greek terms. For years, I have been puzzled by English translators’ seemingly random alternations between respective uses of power, potentiality, and possibility for what was supposed to be the “same” concept in Aristotle. Aubry’s highlighting of the Greek words tells me I should have long ago studied this more carefully with the side-by-side Greek and English texts in the Loeb edition. The translators’ alternations are probably not random at all, just not commented upon. We are not dealing here with things confusingly said of one same concept, but rather with things more clearly said about each of several related concepts. This is just the kind of disambiguation that Aristotle himself pioneered.

“Book Delta defines [the possible] differently, as that of which the contrary is not necessarily false; that which is true; that which can be true. Thus characterized without relation to dunamis, dunaton no longer means having power, but possible. Delta opposes it to the impossible, adunaton, defined as ‘that of which the contrary is necessarily true’ (for example, the commensurability of the diagonal of a square with its sides), and distinguishes the possible and the impossible thus defined, from power (dunamis) and the lack of power (adunamia)” (ibid).

“Nevertheless, the definitions of Delta again carry an equivocity: in its second sense (that which is true), the possible includes the necessary, or what cannot not be: according to the first and third definition, on the other hand, it is identified with the contingent (to endekhomenon). It is this last sense that is mentioned in Prior Analytics book I: ‘that which is not necessary, and of which one can think that it exists without that leading to any impossibility'” (pp. 124-125).

“The possible is indeed defined sometimes as including, sometimes as excluding the necessary. In its first sense, it can be identified with logical possibility: that is called possible which is not contradictory; the necessary — that which cannot not be the case — can thus be called possible, in the sense that it is true (noncontradictory) to say that it is the case. But the possible can also be identified with the contingent: it thus no longer [indifferently] designates that which cannot not be, or again that which can be this or that. In this second sense, the possible is opposed no longer to the contradictory, but seems to be identifiable with power, understood as the power of contraries (being A or not-A), and of contradictories (being or not being” (p. 125).

We saw previously that both of two contradictories cannot be in act or be the case at the same time, but contradictories can both potentially be in act or be the case.

“The remainder of Theta 4, up to the beginning of Theta 5, nonetheless has the object of opposing determinism. This begins from the distinction between the impossible and the false. A strong determinist position in effect comes back to saying that nothing is possible that is not and will not be true. This position assumes a triple reduction, not only of the possible to the potential and of the potential to the actual, but also of the actual to the true” (p. 126).

This leads back to the position of the Megarians. But Aristotle clearly affirms that the non-actual is not impossible. She quotes, “It is false that you are standing right now, but it is not impossible” (ibid).

Aristotelian potentiality encompasses alternate possibilities.

Next in this series: An Aside on Necessity

Toward a First Cause

Book Kappa (XI) of Aristotle’s Metaphysics briefly reviews material from books Beta (III), Gamma (IV), and Epsilon (VI) about the aims of the ultimate inquiry into first things that is still to be pursued. It also incorporates a brief review of his discussions in Physics books II, III, and V about what motion and change are. Both parts of the presentation here add more explicit hints that we will be looking for something that is both separate and unmoved. These hints are the book’s main interest.

Perhaps surprisingly given its review of content from the Physics, Metaphysics Kappa makes no reference to the detailed argument in Physics book VIII that there is a first unmoved mover of all things, or to the related background about unmoved things in Physics book VII. The beginning of Physics book VIII refers back to “our course on physics”, which is ambiguous, but could imply that it was written later, and possibly after Metaphysics Kappa, which would explain why book VIII’s argument about the first mover is not mentioned here.

“But neither ought one to set down the kind of knowledge being sought as concerning the causes spoken of in the writings about nature, since it is not about that for the sake of which (for this sort of cause is the good, and this belongs among actions and things that are in motion, and it moves things first — for that is the sort of thing an end is — but a thing that first moves them is not present among immovable things). And in general, there is an impasse whether the knowledge now being sought is about perceptible independent things at all, or not, but about other things. For if it is about others, it would be about either the forms or the mathematical things, but it is apparent that there are no forms…. But neither is the knowledge being sought about mathematical things, nor is it a knowledge of perceptible independent things, since they are destructible” (ch. 1, Sachs tr., pp. 205-206).

This passage is interesting in a couple of ways. The knowledge being sought in the inquiry to be conducted is now more definitely said to be not about perceptible independent things, not about mathematical things, and not about Platonic forms.

He also points out that what he calls physics is concerned primarily with what he calls sources of motion and change. It does not address questions about the good or that-for-the-sake-of which, except in an incidental way. But in Parts of Animals book I, he clearly says that in the overall scheme of things, the good and that-for-the-sake-of-which are more primary than sources of motion. The implication here in Metaphysics Kappa is that the inquiry being prepared for will address them in their own right.

“Also, ought one to set down anything besides the particular thing or not, and is the knowledge being sought about particulars?” (ch. 2, p. 207).

For Aristotle, no universal is an independent thing. The knowledge being sought does seem to be about particulars.

“And there is besides an impasse, that all knowledge is of universals and of the suchness of things, but thinghood does not belong to universal” (p. 208).

Knowledge, however, is concerned with universals. This was the major impasse remaining at the end of book Zeta (VII).

“Now since the knowledge that belongs to the philosopher concerns being as being universally and not in relation to a part, … if it is meant in accordance with something common, it would be subject to one knowledge. It seems to be meant in the way that has been spoken of, in just the way that medical and healthy are meant” (ch. 3, p. 209).

He refers back to the discussion of how the saying of being in the other categories points back to the saying of substance-essence-thinghood.

“Since all being is meant in accordance with something that is one and common, even though it is meant in a number of ways, … such things are capable of being subject to one knowledge” (p. 211).

This enables us to say that there is after all one knowledge that can be said to be of being as such. It will address the proper saying of substance-essence-thinghood directly, and the proper saying of being in the other categories in a derivative way.

“And since the mathematician uses common notions in a particular way, it would also belong to the primary sort of philosophy to study the things that govern these” (ch. 4, p. 211).

He seems to assert in passing that first philosophy includes what we would call the foundations of mathematics. Elsewhere he mentions that the first principles of mathematics are similarly supposed to be applicable to all things. But mathematics does not address what things in general are in their own right.

“And it is the same way also with the knowledge about nature as with mathematics, for physics studies the attributes and sources of beings insofar as they are in motion and not insofar as they are, (but we have said that the primary sort of knowledge is about these things to the extent that the things underlying them are beings, but not insofar as they are anything else). For this reason one must set down both this sort of knowledge and the mathematical sort as parts of wisdom” (pp. 211-212).

Neither mathematics nor what Aristotle calls physics addresses substance-essence-thinghood, or what things are in their own right. It is left to first philosophy to do this, as well as to inquire into the ultimate principles that underlie mathematics and physics.

Just as in book Gamma (IV), Aristotle’s claim that there is after all a knowledge that applies to all being as such, and that the philosopher is the one who has it, is immediately followed by a somewhat lengthy expression of outrage against those who claim a right to contradict themselves, or deny that there is any such thing as contradiction. Just as in book Gamma, the concerns he expresses are about dialogue, the understanding of meaning, and the possibility of sound reasoning.

This makes perfect sense when we recall that Aristotle has consistently treated being in a transitive way, as always being this or being that; and as intimately involved with saying, especially the saying of what things properly are in their own right. He has at the same time treated saying as meaningful saying, intimately involved with reasoning. So we should not be surprised when it turns out that the knowledge that applies to all being as such has to do with fundamental principles and presuppositions of reasoning and the understanding of meaning.

“Now those who are going to participate in a discussion with each other must in some way understand what they say…. It is necessary then for each of the words to be intelligible and to mean something, and not many things but only one, but if it does mean more than one thing, it is necessary to make clear to which of these one is applying the word. So the one who says ‘this is and is not’ denies that which he says, and so he denies that the word means what it means, which is impossible” (ch. 5, p. 212).

Then he again expresses outrage at what he takes to be Protagoras’ claim that truth is entirely subjective. If this were the case, there would be no being as Aristotle understands it. Being “in its own right” is discursively communicable intelligibility.

“Something closely resembling these things being discussed is what was said by Protagoras, for he said that a human being is the measure of all things, meaning nothing else than that what seems so to each person is solidly so” (ch. 6, p. 213).

“And since it is necessary for each sort of knowledge to know in some way what something is, … one must not let it go unnoticed in what way the one who studies nature needs to define it and how he needs to get hold of the articulation of the thinghood of things” (ch. 7, p. 217).

The inquiry to be pursued here is implicitly presupposed by physical inquiries. To the extent that one of these two, taken in itself, governs the other, taken in itself, the inquiry to be pursued here is more primary than physics (or mathematics).

“Now the study of nature is about things having a source of motion within themselves, while mathematics is contemplative and concerns something that remains the same, but is not separate. Therefore, about the sort of being that is separate and motionless, there is another sort of knowledge that is different from both of these, if there is any such independent thing — I mean something separate and motionless — which is just what we shall try to show. And if there is any such nature among beings, that would be where the divine also is, and this would be the primary and most governing source of things. It is clear, then, that there are three classes of contemplative knowledge: physics, mathematics, and theology” (ibid).

What he calls nature is a source of motion within something “as itself” (all other sources of motion he calls potentialities).

Now he explicitly mentions that he intends to show that there is a kind of being that is both separate and motionless, as he understands these two terms. He says that if there is such a thing, it will be “where the divine is”, and it will be “the primary and most governing source of things”. First philosophy will therefore be alternately characterized as theology.

He returns to the impasse about knowledge in first philosophy. “One might be at an impasse whether the knowledge of being as being ought to be set down as universal or not” (p. 218). Knowledge is supposed to be concerned with universals, but we are seeking an independent thing, and no logical universal is an independent thing.

In the earlier suggestion of a solution to this impasse, he re-interpreted the many ways in which being is said for the different categories, re-describing them as multiple derivative meanings pointing to one primary meaning. This seemed to eliminate the need to refer to a universal that abstracts over the ways being is said for the different categories.

Now he complements this by introducing a new way of speaking universally, which does not depend on abstraction. Instead, universality can be achieved by referring to a concrete thing or things that is or are concretely the cause or causes of all things, and that therefore is or are prior to all the rest.

“So if natural independent things are primary among beings, then also physics would be the primary sort of knowledge; but if there is another nature and independent thing that is separate and motionless, it is necessary that the knowledge of it be other than and prior to physics, and universal by being prior” (ibid).

Everything that Aristotle calls independent, he also calls separate. Also equivalent to these is calling something a this. As noted earlier, the challenge is to find something that is independent and separate and a this, but that is also unmoved in his sense. The impasse about universality will be conclusively resolved by finding something that is universal not in the sense of being abstract, but rather, as he says, universal in the sense of being “prior” to all other things, because it is a cause for all of them.

“And that, of what is so incidentally, there are not causes and sources of the same sort as there are of what is so in its own right, is clear, for then everything would be by necessity” (ch. 8, p. 219).

As he said in book Zeta (VII), the contingency of incidental being must have contingent, incidental causes. Now he relates this more specifically to a consideration of that-for-the-sake-of-which.

“That which is for the sake of something is present in things that happen by nature or as a result of thinking, but it is fortune when any of these happen incidentally, for just as being is in one way in its own right and in another way incidental, so also with cause. And fortune is an incidental cause in the things that are by choice, among those that happen for the sake of something, for which reason fortune and thinking concern the same things, since there is no choice apart from thinking…. And since nothing incidental takes precedence over things in their own right, neither then do incidental causes, so if fortune or chance is a cause of the heavens, intelligence and nature have a prior responsibility” (pp. 219-220).

There is such a thing as fortune or things happening by chance, but “intelligence and nature have a prior responsibility”, just as what things are in their own right takes precedence over things that are the case incidentally.

“Something is in one way only as at-work, in another way as in potency, and in another way both in potency and at-work, and again in one way as a being, in another as a so-much, in other ways in the rest of the categories; and there is no motion apart from things, since something changes always according to the categories of being, and there is nothing common to these which is not within a single category” (ch. 9, p. 220).

Every change is understood by Aristotle as a change with respect to one of the categories. What is common to these is not an abstraction, but the single concrete sense for one category (substance-essence-thinghood), from which the senses for the other categories are derived.

Here he mentions being in the sense of potentiality and actuality, before he mentions being in the senses of the categories. Next, he summarizes the Physics‘ account of motion. “Motion” is the (incomplete) actualization of a potentiality, where actuality or being-at-work or fulfillment would be its complete actualization.

“So the being-at-work-staying-itself [entelechy, identified by Aristotle with actuality or being-at-work or fulfillment] of what is in potency, whenever it is at-work as a being-at-work-staying-itself, not as itself but as movable, is motion” (p. 221).

“And the reason for motion’s seeming to be indefinite is that it is not possible to place it as a potency or as a being-at-work of beings, for neither is what is capable of being so-much necessarily in motion, nor what is actively so-much; and motion seems to be a certain sort of being-at-work, but incomplete, and the reason is that the potency of which it is the [complete] being-at-work is itself incomplete. And for this reason it is hard to grasp what it is, for it is necessary to place it either as a deprivation or as a potency or as an unqualified being-at-work, but none of these seems admissible; so what remains is what has been said, both that it is a being-at-work and that it is the sort of being-at-work that has been described, which is difficult to bring into focus but capable of being” (p. 222).

Motion is an incomplete actuality or being-at-work or fulfillment. This is a rather subtle thought, the grasping of which requires that we first understand that-for-the-sake-of-which, actuality, and potentiality. (Motion in the modern sense, on the other hand, has no teleological significance. It is entirely reducible to measurable quantities. It it not that one of these is “right” and the other “wrong” — they are two different concepts, grounded in different kinds of explanation.)

“And it is clear that motion is in the movable thing, for it is the being-at-work-staying-itself of this by the action of the thing capable of causing motion. And the being-at-work of the thing capable of causing motion is not different, since it is necessary that it be the being-at-work-staying-itself of both; for a thing is capable of causing motion by its potency and is in motion by being-at-work, but it is capable of being-at-work upon the thing moved, so that the being-at-work of both alike is one, just as the interval from one to two and from two to one is the same, and the uphill and downhill road, though the being of them is not one, and similarly also in the case of the thing causing motion and the thing moved” (ibid).

Motion for Aristotle is always said to be in the thing moved, not in the mover. The potentialities of mover and moved with respect to any motion are said to be one.

“Now it is not possible for the infinite to be something separate…. Also, how could the infinite admit of being something in its own right, if number and magnitude, of which the infinite is an attribute, do not?…. And it is clear that it is not possible for there to be an infinite actively…. [T]hat there is no infinite among perceptible things is clear…. [N]or could there be a number that is separate and infinite, since a number or that which has a number is countable…. In general it is impossible for there to be an infinite body and a place for bodies” (ch. 10, pp. 222-224).

As he argues in greater detail in the Physics, there is no “separate” or “actual” infinite.

“[T]here is something that is moved primarily on account of itself, and this is what is moved in its own right. And this is the same way also with the thing that causes motion, for it does so either incidentally, or on account of a part, or in its own right” (ch. 11, p. 225).

There is something that is a mover in its own right.

“But the forms and the attributes…, such as knowledge and heat, are motionless; it is not heat that is a motion but the process of heating. Change that is not incidental is not present in all things but in contraries and what is between the and in contradictories, and belief in this comes from considering examples” (ibid).

For Aristotle, it is only composite things (i.e., those he understands as formed from material) that are subject to motion and change. In his sense, for instance, a composite thing may undergo a process of becoming warmer, and that would be a kind of motion of the thing. But heat itself is not a composite thing. (That heat itself does not move would be true even under the modern interpretation of it as the amount of molecular motion within a material.)

“A thing that changes does so either from one underlying thing to another, or from what is not a subject to what is not another subject, or from what is not a subject to that subject (and by ‘subject’ I mean what is declared affirmatively), so that there must be three kinds of change, since that from what is not one subject to what is not another subject is not a change, for they are neither contraries nor is there a contradiction, because there is no opposition between them” (ibid).

“And since every motion is a change, and the kinds of change mentioned are three, but those that result from coming-into-being or destruction are not motions, and these are the changes between contradictories, it is necessary that change from one subject to another be the only sort of change that is motion” (p. 226).

A “subject” here is just some thing that underlies something else that has the character of an attribute. I would infer that the change from one subject to another that is spoken of here is a reference to the way that something that is potentially X becomes actually X by the action of something else that is already actually X, as the parent of a child and the Platonic “model” of an artifact were said to be.

“So if the ways of attributing being are divided into thinghood, quality, place, acting or being acted upon, relation, and quantity, there are necessarily three kinds of motion, with respect to the of-what-sort, the how-much, and the place. There is no motion with respect to thinghood, because nothing is contrary to an independent thing, nor of relation …, nor is there a motion of acting and being acted upon, nor of moving and being moved, because there is not a motion of a motion or a coming into being of coming into being, or generally a change of a change…. For every motion is a change from one thing to another, and this is also with coming into being and destruction, except that these are changes into one sort of opposites, while motion is a change into another sort” (ch. 12, pp. 226-227).

The modern concept of acceleration is not a “change of a change”, but a change in a rate of change. Surprisingly, he does not seem to mention change with respect to place, or locomotion, here.

“Also, it would go to infinity if there were to be a change of a change and a coming into being of coming into being…. And since of infinite things there is no first one, there would not be a first becoming, and therefore no next one either, and then nothing would either come into being or be moved or change” (pp. 227-228).

Here as elsewhere, Aristotle is anxious to avoid any form of infinite regress. Showing that there is a separate, unmoved, everlasting thing that moves others is what will enable him to do that. That will be the main task of book Lambda (XII).

Next in this series: Pure Entelechy

Being as Such?

Aristotle begins book Gamma (IV) of the Metaphysics by saying that after all, “There is a kind of knowledge that contemplates what is insofar as it is, and what belongs to it in its own right” (ch. 1, Sachs tr., p. 53).

To understand what this really means, we need to consider book Gamma as a whole, also taking into account in advance Aristotle’s disambiguation of “being” and “is” in book Delta (V). (There is another enumeration of the meanings of being in book Epsilon (VI), but it is does not really add anything to the one in book Delta.)

Here in book Gamma, he adds the new element that “Being is meant in more than one way, but pointing toward one meaning and some one nature rather than ambiguously…. just as every healthful thing points toward health…. For some things are called beings because they are independent things, others because they are attributes of independent things, others because they are ways into thinghood, or destructions or deprivations or qualities of thinghood, or are productive or generative of independent things, or of things spoken of in relation to independent things, or negations of any of these or of thinghood, on account of which we say even nonbeing is nonbeing. So just as there is one kind of knowledge of healthful things, this is similarly the case with the other things as well” (ch. 2, pp. 53-54).

Classically, “said in many ways” means said homonymously, like “flies” in “Time flies like an arrow” and “Fruit flies like bananas”. The same sound and spelling are used for different meanings that have no discernible relation to one another.

The comparison to health gives a pretty clear indication of what he wants to say here. But the “one thing” that is pointed to in the same way that health is pointed to is not “being”, but rather the concept of what Sachs calls independent things (“substances”).

In the disambiguation in book Delta, Aristotle says “just as many things are said to be in their own right as are meant by the modes of predication”. This is an allusion to the various ways in which things are said, which are enumerated and discussed in an elementary way in the Categories. Ousia (“substance”, or what Sachs calls “independent thinghood”) has a somewhat privileged place in this enumeration — we might say, just because it is the one that the others “point” to. Ousia will later turn out to be the “what it is” or “what it was to have been” of a thing.

The uses of “is” that he mentions are exclusively the transitive ones. He does not even mention any case like “Socrates is, full stop”. There is absolutely no mention of an “is” of existence, as opposed to the “is” of saying something about something. Saying something about something is the only role of “is” here, and this is strongly borne out by the remainder of the text of book Gamma.

Saying the what-it-is of something of that thing is for Aristotle the central, focal way of saying something about something in general. The other ways of saying something about something form what linguists might call a family of metonymies clustered around the saying of what-it-is. Metonymy involves indirectly referring to a thing by referring to one of its attributes. By contrast, Aristotle takes the what-it-is to refer directly to the thing (which is probably why Sachs calls the what-it-is the “thinghood” of the thing).

All the ways of saying something about something have in common that they are ways of saying something about something. In Sachs’ language, they are “modes of predication”. But the saying of what-it-is serves as a kind of paradigm for the rest.

The main body of book Gamma is actually a long polemic against the Sophists and the friends of Cratylus. It is about the conditions of rational discourse.

A number of the Sophists outraged Aristotle by making flagrantly self-contradictory assertions, and claiming a right to do so. Very uncharacteristically, Aristotle seems to lose his cool over this. He goes on and on about it, beating the dead horse into the ground. He does so because for him this is a violation of fundamental ethics.

To deliberately assert something and its contrary, or to claim a right to do so, is not just to talk nonsense. Aristotle implies it is deeply immoral — the deepest possible violation of intellectual integrity and the integrity of thought. As he says, it is completely impossible to have dialogue with someone who insists on this, and dialogue is the foundation of reason. For Aristotle, such a person hardly even qualifies as human.

Kant and Hegel treat unity of apperception not as something that spontaneously happens, but as the fulfillment of an ethical norm. When we commit ourselves to something by asserting it, we are then also morally committed to the assertion of what follows from it, and even more so to the denial of what is contrary to it. Aristotle’s outrage shows how strongly he shares this point of view.

The friends of Cratylus were radical Heracliteans. Heraclitus famously said that all things flow, and you cannot step in the same river twice. Cratylus claimed it would be more correct to say you cannot step in the same river once. Effectively, this means there is no such thing as being the same at all, so “same” has no real meaning. But if there is no sameness, there can be no contradiction, because contradiction is saying contrary things about the same thing. So the friends of Cratylus too ended up justifying what we would regard as self-contradictory statements.

So when Aristotle is concerned to assert that there is after all a knowledge of being as such and that it is the business of the philosopher to have it, all the evidence in book IV leads to the conclusion that what he is really saying is that the philosopher doesn’t just believe but knows that contraries are not true of the same thing in the same respect at the same time. This is simultaneously a genuine knowledge and a condition of any possible dialogue, a moral imperative as Kant would say.

The only other thing besides the principle of non-contradiction that Aristotle mentions in book IV as applying to being as such is mathematical axioms, which are similarly supposed to be true of all things whatsoever (he does not enumerate them).

Famously, Aquinas read Aristotle’s notion of “pointing toward one meaning” as a kind of analogy. The notion of an analogy of being is better considered as original to Aquinas. Analogy is a symmetrical relationship. If A is analogous to B, we should be able to conclude that B is similarly analogous to A.

But Aristotle’s example of the relation of health to healthful things is not symmetrical; health has a kind of logical primacy over healthful things, and Aristotle very explicitly gives the saying of what-it-is a similar primacy over its metonymic relatives corresponding to the other categories. That is the very means by which he gets from the non-univocity of being to a single concept. That concept is ousia — i.e., “substance”, “essence”, what Sachs calls “thinghood”, or the what-it-is of a thing.

Some commentators have argued that the subject of the Metaphysics is “ousiology”. That seems more accurate than the conventional “ontology”. In any case, Aristotle’s focus is on the conditions of meaningful saying, and especially on saying of what-it-is — not at all on being in the sense of existence.

In the big picture, existence as such is just not an important philosophical concept for Aristotle. What something is and why it is that way are what he is concerned with.

There will be a further level beyond this, in which we will further distinguish the saying of what something is by looking at it in potential and in act, where these terms are understood in a way that is independent of motion, and instead is oriented toward that-for-the-sake-of-which and the good.

Next in this series: Causes and Sources