In my recent philosophical posts, I’ve presupposed a background of Aristotelian metaphysics, but without giving any serious justification for this. In this post, I’ll actually provide a case for the truth of (at least the basics of) Aristotelian metaphysics, starting with the distinction between act and potency. I think these basics are actually pretty intuitive and can be deduced from obvious features of the world, especially the reality of change.
Act and potency
Aristotelian metaphysics is centered around the analysis of change, from which the distinction between act (or actuality) and potency (or potentiality) is deduced. For example, a banana could be actually green and potentially yellow; its potency for yellowness does exist (otherwise it couldn’t become yellow), but not actually (otherwise it would already be yellow). Why should we believe this, rather than just saying that the banana is green now and will be yellow later? To understand Aristotle’s theory of act and potency, we have to look at the alternative views of change held by pre-Aristotelian philosophers.
The Eleatic philosophical school, led by Parmenides of Elea, denied the existence of change. He began from the assumption that there are only two possibilities for a thing: being or non-being. If the banana is green, then the banana’s greenness exists, and the banana’s yellowness doesn’t exist. But nothing can arise from non-existence – ex nihilo nihil fit (“nothing comes from nothing”). Therefore, anything that does not now exist can never exist, and change is impossible. The Heraclitean philosophical school, led by Heraclitus of Ephesus, went to the other extreme and said that only change exists. There’s no such thing as being, only becoming. The green banana ceases to exist when the yellow banana begins to exist, and there’s no “banana” that persists through the change and stays the same.
Both of these views turn out to be self-defeating. According to the Eleatic view, change is an illusion. But this means that Parmenides himself can’t move from considering the premises of his argument to the conclusion; his reasoning process is itself an illusion. According to the Heraclitean view, nothing actually exists for more than a fleeting moment. But then the “Heraclitus” who considers the premises of his argument isn’t the same person as the “Heraclitus” who reaches the conclusion; his reasoning process is also an illusion. Unless change happens and we persist through change, no philosophical argument could possibly be valid.
How can we avoid the self-defeating extremes of the Eleatics and Heracliteans? Aristotle argued against them by denying that only “being” exists (per Parmenides) or only “becoming” exists (per Heraclitus). Instead, between actual existence and non-existence, there is potential existence; “being” (act) and “becoming” (potency) are complementary aspects of reality. This distinction between act and potency is necessary to make sense of change.
While the banana is actually green (i.e., its greenness exists actually), it’s potentially yellow (i.e., its yellowness exists potentially). Because the banana’s yellowness is potential, not non-existent, the banana can turn yellow without anything arising from non-being, contrary to Parmenides. Because the banana’s yellowness is potential, the banana persists through the change from greenness to yellowness, contrary to Heraclitus. The distinction and balance between act and potency, between persistence and change, makes a middle ground possible between the twin errors of Parmenides and Heraclitus.
Aristotle’s distinction between act and potency also helps to solve the classical problem of “the one and the many,” the balance between unity and multiplicity in the world. Parmenides argued that there’s really only one thing in the world, based on a dilemma: if there are multiple things, are they distinguished by being or by non-being? They can’t be distinguished by being, because they share being (i.e., they exist); but they can’t be distinguished by non-being, since non-being doesn’t exist by definition. Therefore, there can only be one thing. Heraclitus’ view, on the other hand, leads to a radical multiplicity in the world. Since nothing persists through change, the things that exist now aren’t the same as the things that exist at any other time.
Once again, the Eleatic view of perfect unity and the Heraclitean view of perfect multiplicity turn out to be self-defeating. If Parmenides is right that there’s only one thing, then the premises and conclusion of his argument are the same thing; his reasoning is an illusion. If Heraclitus is right that the things we experience aren’t really unified or connected to each other across change, then neither are his premises and conclusion really connected to each other.
Aristotle’s view again charts a middle path between these two extremes. By accounting for another kind of being, potential being, in between actual being and non-being, we avoid the two horns of Parmenides’ dilemma and can allow for the existence of multiple things in the world. Furthermore, since the distinction between act and potency allows for the persistence of objects through change, it can allow for the unity of ordinary things over time and across change, contrary to Heraclitus.
In summary, the distinction between act and potency is necessary to make sense of the reality of change, persistence, unity, and multiplicity. In contrast to the Eleatic school’s claim that only “being,” persistence, and unity are real, and the Heraclitean school’s claim that only “becoming,” change, and multiplicity are real, Aristotelians can accept the reality of all these things. This is because act (or actuality) serves as the principle of persistence and unity, while potency (or potentiality) serves as the principle of change and multiplicity. Any attempt to deny the reality of either act or potency is ultimately self-defeating.
The reality of essence
The ideas of essences and powers are also central to Aristotelian metaphysics. A power is a disposition of a thing for change. These can be divided into active powers, which are dispositions to cause changes in other things, and passive powers, which are dispositions of a thing to be changed in some way. A thing’s potencies are directed toward specific actualities, giving it certain dispositions. The essence of a thing is what a thing is, from which its particular properties and powers flow. (The term “essence” is translated from Aristotle’s phrase to ti ēn einai, literally, “the what it is to be.”) These ideas are seen by many non-Aristotelians as pre-scientific or even anti-scientific. However, for the Aristotelian, they’re actually necessary for and presupposed by all scientific inquiry.
To understand why essences and powers must really exist, let’s look at the laws of nature. What do these laws actually describe? There are three logically possible answers: either they describe something external to nature, internal to nature, or neither external nor internal to nature.
Extrinsic to nature
There are two ways that the laws of nature could be something extrinsic to nature: by reference to God (i.e., something personal outside of nature) or some kind of Platonic forms (i.e., something impersonal outside of nature).
Let’s take the first option. On this view, laws of nature just describe what God does, so gravity describes that God moves things with mass toward each other at a rate consistent with our equations (F = G * m1 * m2 / d^2). This entails that physical things are causally inert – they don’t actually do anything, it’s God who does everything. The sun doesn’t melt an ice cube; God causes the ice cube to melt when the sun comes out. This view is called occasionalism. Taken to its logical conclusion, occasionalism seems to entail something like pantheism; since our observations rely on the laws of nature, we don’t actually observe anything as it really is, but how God causes it to appear to us. This is bad theology.
It’s also bad science. The goal of science is to discover things about nature; but on this view, we can never discover anything about nature itself (which is causally inert), merely the different ways that God acts. Furthermore, it gives us no reason to think that the laws of nature will be consistent over time. This is because the ‘laws’ don’t actually describe anything about nature itself, but instead how God has chosen to act, and it’s conceivable that he could act otherwise.
What if we take the second view? According to Platonic metaphysics, things in nature have properties by participating in higher-level forms. Things have mass insofar as they participate in the Form of Mass. Laws of nature, likewise, are explained by participation in forms; so just as massive things participate in the Form of Mass, they also participate in the Form of Gravity, which corresponds to our equation (F = G * m1 * m2 / d^2).
But this leads to an explanatory problem: why do things participate in these forms rather than others (for example, the Form of Schmavity which says that massive things repel each other)? We can explain this with reference to even higher-level forms, and so on, but unless the explanation bottoms out in something else, we have a vicious infinite regress that doesn’t really explain anything. Perhaps it can be explained by something personal outside of nature – but this leads us back to theistic occasionalism. Perhaps it can be explained by something intrinsic to nature, or it’s simply a brute fact – but this leads us to one of the other two explanations (see below). Any way you slice it, Platonic forms can’t explain the laws of nature.
Neither extrinsic nor intrinsic
Maybe the laws of nature aren’t explained by anything extrinsic or intrinsic to nature. They could just describe regularities that we observe across nature, but nothing deeper explains these regularities. This view has a few serious problems. First, it makes the laws of nature a brute (unexplained) fact, which violates the Principle of Sufficient Reason: that every fact which could have an explanation does have an explanation. If the PSR is false, our sense data and/or our conclusions from that data could simply have popped into our mind for no reason whatsoever. Denying the PSR makes science and all empirical investigation impossible, so the ‘mere regularity’ view of laws of nature is self-defeating.
Second, this view makes the laws of nature only dependent on our past and present observations, and therefore can’t predict anything about the future. To riff off the famous (in philosophy) “grue” paradox, let’s say that there’s a property schmass, and things with schmass exhibit schmavity: they attract other things with schmass before January 1, 2050, after which they repel them. Can our observations tell us whether things have mass or schmass? No, because all of our observations (so far) have taken place before January 1, 2050! Thus, if the ‘laws of nature’ merely describe regularities that we observe, and nothing deeper about nature, we can’t know if they’ll fail in the future, which makes scientific inquiry impossible.
Finally, the laws of nature aren’t regularities. For gravity, no two masses ever exist in complete isolation from all other forces. The equation F = G * m1 * m2 / d^2 tells us what would happen if, counterfactually, two masses existed apart from all other forces. The same is true of other laws of nature, like Coulomb’s law (no charged particles exist in isolation from all other forces). The laws of nature describe tendencies that things exhibit, which can be masked by counteracting influences. Therefore, the ‘mere regularity’ view fails on all counts.
Perhaps, as some philosophers of science (such as Nancy Cartwright) argue, the laws of nature don’t really exist at all; they’re just ‘convenient fictions’ that we use because they help us make accurate predictions. If so, it would be truly miraculous that every single mass we see consistently attracts all other masses according to the same equation (and the same goes for the other laws of nature). This view can be rejected just because of its improbability. To be sure, our understanding of the laws of nature could change in the future with a new scientific theory, but there must be something that explains the otherwise miraculous regularities we see in nature.
Intrinsic to nature
By process of elimination, the laws of nature must be something intrinsic to nature. This is also the most common-sense view (at least to me): we assume, when we’re doing science, that we’re actually discovering something about the things we’re studying. We’re not discovering something about God or about Platonic forms, and we’re not describing mere regularities or inventing ‘convenient fictions.’
To continue with the example of gravity, this refers to a disposition within the massive thing itself, namely its disposition to attract other masses to itself (an active power) and to be attracted to other masses (a passive power). What’s true of gravity is true of the other laws of nature, which also describe active and passive powers of natural things. The potencies of natural things are indeed directed toward specific actualities. And the fact that things have specific powers that remain consistent over time – for example, an electron has a particular mass and charge – is explained by its essence. Therefore, even hyper-reductionist physicalists, who think that fundamental particles are the only real objects, should admit the existence of powers and essences.
In summary, rather than being merely pre-scientific (much less anti-scientific), the Aristotelian concepts of powers and essences are presupposed by science. Science seeks to discover what things are (i.e., their essences), and how they act under controlled circumstances (i.e, their powers in the absence of masking influences). Furthermore, despite the reductionist approach taken above, this is true not only of particle physics but also of larger chemical and biological systems, which have powers that aren’t reducible to those of fundamental particles. (The Stanford Encyclopedia of Philosophy article on the philosophy of chemistry refers to an “anti-reductionist consensus in the philosophy of chemistry literature”.)
The reality of causation
The above argument for powers is also an implicit argument for the reality of cause and effect. After all, an active power (disposition to cause a change) is precisely a disposition to produce some effect, and a passive power (disposition to be changed) is a disposition to be caused in some way. However, some philosophers argue that the cause-effect relationship is only conceptual, and there’s no such thing as causation in the real (extra-mental) world.
Hume vs. causation
David Hume famously argued, based on empiricism, that causation doesn’t exist because we never observe anything causing anything else – we merely observe regular correlations between things. Hume defined a ‘cause’ as “an object, followed by another, and where all the objects similar to the first, are followed by objects similar to the second” (Enquiry VII.2), but this connection between ‘cause’ and ‘effect’ is based on our observations and is entirely conceptual. For example, every time we see a rock thrown toward a window, it’s followed by the window breaking, so we call these things ‘cause’ and ‘effect’; but it’s logically possible that a rock being thrown toward a window could lead to something else, like the rock passing through the glass without breaking it.
This view that the cause-effect relationship is only a regular correlation falls prey to the same fatal problems as the ‘regularity’ view of laws of nature described above. If causation merely describes regularities in our observation, then (1) the regularity is a brute fact, (2) the regularity could fail at any point in the future, and (3) it’s unable to explain why some causes only sometimes produce their effects (for example, quantum indeterminacy). Still, Hume puts forth an argument for the non-reality of causation (Treatise I.3.3):
1. Whatever is distinguishable can be conceived to be separate from each other.
2. The cause and effect are distinguishable.
3. Therefore, the cause and effect can be conceived to be separate from each other.
4. Whatever is conceivable is possible in reality.
5. Therefore, the cause and effect can be separate from each other in reality.
In other words, we can conceive of a window breaking for no reason whatsoever, and we can conceive of a rock being thrown at a window without breaking it. What we can conceive of is logically possible in reality. Therefore, it’s possible for the cause (rock being thrown) and effect (window breaking) to be separate in reality. This is true of all causes and effects, which means that ‘causation’ is only a regular correlation.
But this argument has a few problems. Just because some things are conceivably separable doesn’t mean that they’re really separable. We can conceive of the radius of a circle separately from its circumference, and the sides of a triangle separately from its angles, but neither of these pairs can really be separated. Second, the classical concept of causation is simultaneous, not consecutive; the relevant cause and effect in our example aren’t just the rock being thrown and the window breaking, but the rock pushing through the window and the window giving way to the rock. It’s not at all clear that these last two things can be imagined separately.
Finally, can we imagine the window breaking with no cause? Even if we imagine it breaking without anything hitting it, maybe it broke due to external stresses we couldn’t ‘see’ (imagine). This might sound pedantic, but the entire argument is based on imagination. Trying to imagine something happening for truly no reason whatsoever stretches the limits of the imagination, and it might not even be possible. Therefore, Hume’s argument against the reality of causation fails, or at least, it’s very plausibly unsound.
Russell vs. causation
Bertrand Russell also argued against the reality of causation in his 1913 paper “On the Notion of Cause, with Applications to the Free-Will Problem.” He argued (in part) that because the notions of “cause” and “effect” can’t be represented in physics equations, they aren’t necessary to make sense of the world, since the world is described by physics. Even more importantly, there is a temporal asymmetry between cause and effect (cause comes before effect), but there is no such asymmetry in physics equations, so causation is ruled out as a possibility (at least at the microphysical level).
The first part of his argument is simply a non sequitur. Just because something isn’t represented in physics equations doesn’t mean it isn’t a real aspect of reality, as Russell himself went on to argue (in his 1959 book My Philosophical Development). In his own words, “All that physics gives us is certain equations giving abstract properties of... changes. But as to what it is that changes, and what it changes from and to — as to this, physics is silent.” As we saw above, any robust account of the laws of nature has to involve causal powers, so even though causation isn’t represented in physics equations, it is presupposed by them.
The second part of the argument is more serious. It shows that temporally asymmetric notions of causation won’t work in physics. When two charged particles are attracted to each other, it’s impossible to say that one particle’s attraction of the other happened before the other particle’s movement. But this doesn’t show that causation isn’t involved; it shows that this causation must be simultaneous, which is perfectly in line with the Aristotelian notion of causation. The related objection that quantum mechanics shows causation isn’t real, because of indeterminacy at the quantum level, likewise misses the mark since causes don’t necessitate their effects on the Aristotelian account.
Finally, even if it were true that causation is irrelevant to physics, this doesn’t change the fact that causation is very important in other sciences like chemistry and biology. At the most, Russell’s argument would show that these other sciences are irreducible to physics, which Aristotelians agree with.
The principles of causality
We’ve now seen that causation must be a real feature of the world. Furthermore, Hume’s and Russell’s arguments suggest that causes are simultaneous with their immediate effects, which is an important part of the Aristotelian notion of causation. There are two further principles of causation that Aristotelians affirm:
Principle of Causality (PC): A potential can only be actualized by something that is actual.
Principle of Proportionate Causality (PPC): Whatever exists in an effect must exist in some way in its total cause.
Why should we accept these principles? Well, PC follows from the Principle of Sufficient Reason, that every natural fact has an explanation. According to PSR, a potency being actualized must be explained by something, and it can’t be explained by itself or any other potency, since mere potencies (like an unripe banana’s potential to be yellow) can’t actualize anything by definition. Therefore, a potency can only be actualized by something already actual. PC is as certain as PSR, and as I noted above, PSR is pretty certain – otherwise empirical and rational investigation would be impossible, since our sense data and beliefs could happen for no reason whatsoever.
PPC sounds more controversial than PC, but it’s really not if properly understood. PPC doesn’t say that whatever exists in an effect must exist in the same way as in the cause, only in some way. It could exist in the same way in the cause (i.e., “formally”), such as if I have a twenty dollar bill that I give you. It could also exist in a different way in the cause (i.e., “virtually”), such as if I have twenty dollars in a savings account and allow you to withdraw my twenty dollars as cash from an ATM. It could exist in the cause as a power to produce it (i.e., “eminently”), such as if I have the power to print a new, genuine twenty dollar bill for you.
With this in mind, PPC also follows directly from PSR. If something in an effect doesn’t exist in any way in the cause – not even eminently, as a power to produce it – then it has no explanation. There would be a potency that was actualized without anything to actualize it. It would be as if I told you I could give you a genuine twenty dollar bill, but I had no cash, no money in any other form, and no power to print any genuine money.
Final causality
So far, we’ve only talked about what Aristotle referred to as efficient causes. An efficient cause of a change is the agent of the change, the thing which actualizes a potential; this is what we usually mean today when we talk about a “cause.” But efficient causes are directed toward particular ends, which Aristotle refers to as the final cause of their effects – “that for the sake of which a thing is done” (Physics II.3). Without final causes, efficient causes could produce no specific effects, since there would be no terminus of the changes that they cause. These final causes are the 'directionality' or 'intentionality' of a thing's potencies toward their specific actualities.
This is controversial in modern philosophy, but it’s also necessary to make sense of the regularities we see in nature. Things obviously have dispositions to produce particular effects. For example (to return to the laws of nature), masses attract other masses, and negative charges attract other negative charges and repel positive charges. Based on our earlier argument for the reality of powers, these dispositions must be intrinsic, not ‘mere regularities’ or something imposed from the outside. This is exactly what Aristotle means by “final causes.” Therefore, just like powers, final causes are actually presupposed by science.
Conclusion
To sum up what we’ve seen so far: Based on features of the world like change, persistence, unity, multiplicity, regularity, and causation, we can deduce the basics of Aristotelian metaphysics like the distinction between act and potency and the reality of powers, essences, and efficient and final causes. Although many philosophers have tried to deny the reality of these features of the world, these views ultimately end up being self-defeating, and undermine any empirical or rational pursuit of knowledge. What else can we deduce about the world using these basics of Aristotelian metaphysics? That’s what we’ll look at next time.
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