Phil 101: Substances, Monism, and Dualism

As we mentioned in our sketch of basic ontology, substances are understood to be a special kind of concrete individual thing.

“Substance” is sometimes used in the sense of “chemical substances,” or to mean “the stuff you’re made of.” For example, I have a statue of Frodo Baggins, and it’s made of clay. The substance this statue is made of is clay. (Some philosophers would argue that the statue and the clay are one and the same thing, others wouldn’t.)

But there’s a more dominant use of “substance” in philosophy to mean something a bit different. It’s trying to capture a notion of individual things-with-a-capital-T, things that really deserve to be called “Things,” in a robust, full-blooded sense. As opposed to when you’re just talking about “ten things that annoy me,” where some or all of those things may not.

Terminological background: Greek philosophers had a word ousia—which is a form of the verb to be and is connected to our term “ontology”—that these philosophers used in a special way. This word was translated into Latin as essentia and/or substantia. Some authors used one translation, others used the other, and some used both. Centuries later, English has inherited the words essence and substance. Over thousands of years and many philosophical debates, these different terms shifted and sharpened their meaning in some ways. In modern and contemporary philosophy, “essence” and “nature” are used to mean one sort of notion, and “substance” another.

Here we’ll focus on how philosophers nowadays understand the notion of “substance.”

“Modern philosophy” means from about 1600-1800. “Contemporary” philosophy means from about 1900 until now.

Not every philosopher wants the category of substances in their map of reality. But those who do understand substances like this.

In the first place, they are individual things, rather than properties or relations. They are the sorts of things that have properties, rather than being ways that other things are qualified. Indeed, as we’ll discuss below, substances are often taken to be the “fundamental bearers of properties,” in some sense. Neither would we count facts or events as substances.

In the second place, substances are taken to be concrete: unlike, say, numbers or general shapes. Saying they are concrete does not mean that substances must be physical or exist in space and time; though many philosophers will argue that the only substances that really exist are physically located. But this needs to be argued for. It’s not part of the definition or concept of what a substance or concrete individual needs to be.

We said that substances are understood to be a special kind of concrete individual. Special in what way? Let’s consider some examples.

Consider the following sentences.

Mel has a sharp knife. Mel has a sharp wit.
Once you climb the steep cliffs on this side, you'll find a gentle hillside sloping down to the plain. Despite his harsh words, Derek has a gentle touch.
My cellphone has a bright light. Persephone has a bright smile.

Sharpness is a property that can be had by both knives and wits, but knives and wits seem to be fundamentally and importantly different from each other.

Similarly, gentleness is a property that can be had by both hillsides and touches, but hillsides and touches seem to be importantly different.

Lights and smiles also seem to be importantly different.

The notion of a substance is a philosophical tool for unpacking these differences.

Words like “wit” and “touch” and “smile” are nouns. We can call the things they describe “things” in some sense. After all, you’d easily say, “Your knife may be sharp; but something that’s even sharper is my wit.” Notice you said “something.” Or “One thing she likes about you is your sharp wit.” But it’s also natural to have the sense that knives and hillsides and lights are Things in a deeper or more basic sense than wits and touches and smiles are. That’s the idea that philosophers try to capture with the notion of a “substance.” They’d put this thought by saying: knives and hillsides and lights are substances, but the other things are not.

That’s the basic idea. How we should go on to unpack or elaborate the basic idea is controversial. Some of the things that are often said are:

If you’d like to read more about the notion of substance, and controversies about how to define it, see Howard Robinson’s SEP entry.

These explanations themselves have parts that need explaining. What’s meant by a “fundamental” bearer of properties? What’s meant by “can in principle” and “exist on their own”?

First, let’s note that many philosophers think that something can be a substance even if it’s made up out of smaller substances. They wouldn’t want to deny that mountains or rivers or human bodies or galaxies can be substances, just because they have smaller parts. (Other philosophers will argue that things with smaller parts can’t be substances; but we don’t necessarily have to agree with them. This is a matter for debate. It’s not part of what “substance” means.)

Second, an important idea here is that a knife is the kind of thing that can have properties in itself, intrinsically. The knife either is sharp or it isn’t. Whether it’s sharp might depend on what shape its edge has, but its edge is part of the knife. Once we’ve settled how the knife and its parts are, we’ve settled whether it’s sharp. The knife can also have extrinsic properties, too. It can be further away from me than my cellphone is. But it’s the kind of thing that can have properties on its own.

For Mel’s wit to be sharp, on the other hand, or for Derek’s touch to be gentle, or Persephone’s smile to be bright, these depend on other things having properties. Mel’s wit is sharp only if Mel has certain properties. And Mel is not part of Mel’s wit. For Persephone’s smile to be bright, that depends on the shape of her whole face and how it moves when she smiles. And her whole face is not part of her smile. Thus even if we count wits, and touches, and smiles, as things in some sense, they seem to depend for their existence and character on other things, which are more fundamental. Substances aren’t supposed to depend on anything else (except maybe their own parts).

Now in one sense, Persephone does depend on other things: she needs food, water, sunlight and so on. These things play an important causal role in her continuing to exist (and thrive). But Persephone’s smile seems to depend for its existence on Persephone’s whole face in a more fundamental, logical sense than that. It’s this kind of logical dependence that substances are not supposed to have.

Another example of something that’s plausibly not a substance are waves in ropes or fluids. Consider a particular wave that’s approaching the Wilmington coast right now. On some views, the Atlantic Ocean might be a substance. But many would not count the wave as a substance. It’s just a moving pattern. It depends for its existence on what properties the Atlantic Ocean has. From moment to moment, the wave is made up of different quantities of water as it moves through the ocean. Perhaps it also depends for its existence on the fact that the Atlantic Ocean stops at a certain point and the air above the ocean begins. I don’t know whether the same wave could exist wholly underwater.

So the basic idea is: things like wits, touches, smiles, waves, these may be “things,” but they’re somehow derivative or logically dependent on other things. Things like knives and people and hillsides and lights and oceans are more fundamental. They are better examples of being substances.

It’s controversial what things exactly count as substances. That’s why I’ve hedged a bit and said these are “better examples” of being substances. Some philosophers don’t think there are any substances at all, just properties and/or events. But most do think there are substances. They just disagree about what the substances are.

Here are some things that some philosophers would count as substances. For many of the examples listed here, other philosophers would argue these things don’t really exist, or that they do exist but shouldn’t be counted as substances.

As I said, some philosophers will argue that things with smaller parts can’t be substances. They’d say that the second and fourth examples should be understood more like smiles or waves.

In addition to to those physical substances, some philosophers think there are also non-physical substances:

As we said, it’s not part of the definition of the notion of substance that substances have to be physical or reside in space and time. Nor is it part of the definition of substance that substances have to be measurable or mind-independent. Many plausible examples of substances may have those properties, and some philosophers may argue for the substantive view that things which are physical and measurable are in fact the only substances that really exist. On other views, though, God is a substance that really exists, and some philosophers have even argued that God is the only substance. On other views, God is a substance, and space (or spacetime) is a substance, and everything else (that’s concrete) is just something like a ripple in, or aspect of, one of those two. But most philosophers think there are many substances.

Monists and Dualists

Monists are philosophers who think there is only one kind of substance.

A radical form of this would be that philosopher who thinks there’s just one substance, period, and it’s God.

Another radical form of this would be the philosopher who thinks their own mind is the only substance.

But philosophers who think that God exists and angels exist and many human minds all exist, but nothing else, would also be monists.

All of the philosophers just mentioned think that the only kind of substances there are are mental, non-physical substances. A different way to be a monist would be to say that the only kind of substances there are are ones that physics investigates. Perhaps there are only the basic elements of physics. Or perhaps there are those plus spacetime. Or perhaps macroscopic objects like people and galaxies are also substances. There are different views one could have. But all of these count as broadly materialist or physicalist views.

They are also monists about how many different kinds of substances there are. Just one kind: on their view, though, that kind is physical substances.

Terminological note: “Materialism” was originally the view that everything is made of matter. (Hence the name.) But its usage has broadened so that now you can still be a materialist if you believe in gravitational fields, curves in spacetime, and so on, which definitely are not matter. Basically the materialist believes in whatever our best physics tells us about. Also, I am going to use the terms “materialism” and “physicalism” interchangeably. In some discussions, “physicalism” is instead used for a particular version of materialism.

Also, for the time being, these are only views about what substances there are. There are further debates about what kinds of properties there are; and these debates also leave open what further ontological commitments one takes, such as whether events or numbers exist.

A third group of philosophers disagrees with all of the views just mentioned. These philosophers are dualists. They think there are two kinds of substances: mental, non-physical substances, on the one hand, and physical substances on the other.

These views come in different versions too. One would be the view that says that God is one substance, and spacetime is another, and that’s it. But a more natural view would say that there are many mental substances, and many physical substances. This is the view we’ll be thinking about.

The debate we’re setting up for our next classes is between these kinds of dualists, and philosophers who instead have a materialist/physicalist picture of the mind.

sam brown, explodingdog

On the dualist view, everything that is able to think and feel and be conscious has a non-physical, “immaterial,” purely mental substance associated with it. Philosophers call these souls. They are something like mental or spiritual engines, that are essential to and fundamentally do the thinking and feeling. Souls are separate from the physical world and aren’t made up of any physical parts. (On some views, they’re not made up of mental parts, either; but this is more controversial.)

Perhaps one of the souls is God. What’s we’re going to focus on is that, on the views we’re considering, every human mind also involves a soul. While the body is alive and still functioning properly, the soul is connected to it somehow. It feels things that touch the body, and is usually able to control some aspects of the body’s movement. But it’s possible for the soul to go on existing even after the body is destroyed. In principle, souls can exist independently of bodies or other physical things. (They aren’t like waves or smiles.)

On the materialist view, on the other hand, the only substances there are are physical ones: things like brains and bodies. When these are arranged in the right ways, and have the right kinds of properties, then thinking and feeling and self-consciousness happens. There aren’t any such non-physical substances as what the dualists call “souls.” (Of course, in everyday talk, we’ll often use the word “soul” in a more innocent way, that’s broader than the way the dualist is using it. Materialists can do that too. But in this class, let’s stick to the dualist’s usage.)

Dualists and materialists both get to use words like “minds” and “mental.” They agree that we have mental states and processes — we think, feel, have experiences, are self-conscious, and so on. They have different pictures about what’s needed to explain this. The dualist thinks that mental lives only happen when some immaterial substance, a soul, is involved; it’s what fundamentally has the mental properties and it’s logically independent of and merely in some way connected to physical brains and bodies. A soul doesn’t have physical parts, and in principle, it could still exist even if the physical world went away. The materialist on the other hand denies that there are any substances beyond the physical ones. They’ll have to explain what’s involved in having a mental life in other ways. Different materialists go different ways about how to explain this.

Follow-up Issues

Here are some details we didn’t get to in our class discussion. They will be important in later discussion. For the time being, I’m just going to mention them here, and briefly review them at the start of next lecture. When we get to later parts of the course where these details matter, I’ll remind you that these were mentioned before, and we’ll return to them again and talk about them more.

  1. Are you identical to your soul? Different dualists will give different answers here. Some would say yes. Others would say you are some kind of combination of your soul and your body. These views agree though that in order to think and feel, you need to have a soul. The materialist thinks you don’t.

  2. What substance will a materialist say the mind is?

    It’s natural to think that the materialist will say: since minds aren’t souls, they must be physical substances instead. Perhaps they’ll say that minds are brains; or they might say instead that minds are whole bodies.

    But there’s a more subtle possibility, too. Materialists don’t have to say that minds are any substances. Not a mental substance nor a physical one.

    Consider the notion of a hike. We’ve got some hikers, their clothes, the dirt path they’re walking on, the oxygen they’re breathing, the sweat on their skin. All of those are plausibly substances. But now what substance is the hike? Is it one of them? Is it some combination of them? Is it a further substance, that I neglected to list?

    One option is to say is that the hike isn’t any kind of substance at all. The word “hike” is a noun, but hikes aren’t Things in the same robust, full-blooded, sense that hikers and sweat are. Hikes can’t exist independently. They’re more like waves or processes. So “taking a hike” is fundamentally very different from taking an object, like a ticket. When other things, that are substances, are arranged in certain ways, and have certain properties, then a hike takes place.

    One way to be a materialist is to argue that the mind is a physical Thing or substance, such as perhaps the brain. But another way to be a materialist is to say that talk of minds is like talk of hikes, or smiles, and so on. The mind isn’t any kind of substance. When a person has a mind, there isn’t some specific kind of object we’re saying the person has, neither a physical object nor an immaterial one. Rather, to say a person “has a mind” is just to say that their brain and body can do certain things. They can think; they can have experiences; they can make choices; and so on. When your brain and body can do those things, we say that you “have a mind.” Just as, when your brain and body do other things, we say that you’re “taking a hike.”

    This view of the mind still counts as a materialist view, because they say that the only substances there are are material or physical substances. Thinking and feeling doesn’t involve any extra, immaterial substances in addition to bodies, brains, and whatnot.

    In fact, a dualist can agree that minds aren’t special kinds of substances; what’s crucial to their view is that there are such substances, souls, and that to think and feel and have other mental properties, you need to have a soul. Whether we should say minds are identical to souls, or whether mind-talk is instead like talk of hikes, is something they could have different views about.