21

Locke, Essay II. xii; xiii.1-5; xxii.1-5,9; xxiii.1-11,15-20

Substance

If anyone should be asked, what is the subject wherein Colour or Weight inheres, he would have nothing to say, but the solid extended parts: And if he were demanded, what is it, that that Solidity and Extension inhere in, he would not be in a much better case, than the Indian before mentioned; who, saying that the World was supported by a great Elephant, was asked, what the Elephant rested on; to which his answer was, a great Tortoise: But being again pressed to know what gave support to the broad-back’d Tortoise, replied, something, he knew not what. [Essay II.xxiii.2]

Over Chapters xii-xxviii of the Essay Locke turned from investigating the main simple ideas arising from sensation and reflection to investigating our complex ideas. Complex ideas can arise from one or another of two sources. Simple ideas can be given as bundled together in complexes and compounds in sensory experience and reflection, and this is in fact how all of our simple ideas are originally given to us. But the imagination also has the power to combine simple ideas in ways never encountered in sensory experience. Locke’s main purpose was to show that all of our remaining ideas arise in one or other of these ways, including highly refined and abstract ideas such as those of space or extension, infinity, God, substance, power, and identity. Contrary to what Descartes and others had maintained, these are not “notions” that can only be grasped by the pure understanding but ideas that are well within the powers of sense or imagination to form and that. Indeed, Descartes’s failure to consider how these ideas arise from sense, reflection, and imagination had led him to make serious mistakes about what our ideas of space, infinity, God, matter, and mind involve.

QUESTIONS ON THE READING

1. What is the difference between a complex idea and an idea of relation?

2. Identify two different ways in which simple ideas come to be united in complex ones.

3. What is the difference between a substance and a mode?

4. How do we arrive at our ideas of mixed modes?

5. What gives unity to the various simple ideas in a mixed mode and makes them appear as one, single idea rather than an aggregate of distinct ideas?

6. What conclusion do we tend to draw from the fact that different simple ideas are constantly observed to occur together in our experience?

7. What is our notion of pure substance in general an idea of?

8. What is our notion of particular substances an idea of?

9. What leads us to distinguish material substances from spiritual substances?

10. What is our notion of matter an idea of, and how does it differ from our notion of spirit?

11. What makes one person’s idea of a particular kind of substance more perfect than another’s?

12. What are the primary ideas we have peculiar to body? to spirit?

NOTES ON THE READING

Locke began this project in Chapter xii of Book II by identifying three main the sorts of complex ideas: those that arise from enlarging or compounding the ideas we have received from sensory experience and reflection, those that arise from comparing these ideas and discerning ways in which they resemble or differ, and those that result from isolating simple ideas from the other ideas in whose company they are commonly given. The first of these operations gives rise to our complex ideas, the second to our ideas of relations, and the third to abstract ideas.

Locke went on to divide our complex ideas into ideas of substances and ideas of modes. Somewhat inconsistently (but not at all atypically for him), he also identified ideas of relations as a third type of complex idea, having previously declared them to be a distinct kind of derivative idea. We will set ideas of relations aside for the moment and focus on the other two sorts of complex ideas, those of substances and those of modes.

Substances and modes: “Open-ended” versus “closed-off” complexes. It was noted in the introduction that there are two main sources for our complex ideas. The imagination has the power to combine simple ideas in any way it wants to make complexes. But simple ideas are also presented in compounds and complexes in sense experience and in reflection. According to Locke, when sense experience regularly presents same simple as compounded in the same way, we have a tendency to assume that the regularity is due to the fact that we are being affected by a single object. We think that the single object has various powers or secondary qualities that enable it to simultaneously affect our senses to produce various ideas in us. The ideas are all compounded together because they are all caused by one and the same thing, and so they naturally appear to us as occurring at the same time and as interpenetrating in the same space. When we experience an apple, for instance, we think that there is some one object outside us that affects us with a bundle of ideas of colour, temperature, firmness, scent, and taste that all permeate one another within the same shape.

It is characteristic of these sorts of complex ideas that they are “open ended.” Because we think that the complex is produced by some one object existing outside of us, we can’t be sure that our senses have revealed everything there is to know about it. The object have more powers, and so may be able to bring about more ideas in us, and more changes in other surrounding objects, than at first appears. A gold bar, for instance, may give us ideas of considerable weight, firmness, and yellowness combined within a rectangular shape. But the object can cause more ideas than at first appears. Gold is malleable. That is, it can be deformed (for instance, by hammering) without either breaking to pieces or springing back to its original shape. It is also “fixed,” that is, it does not change into something else when exposed to fire. At the same time, it is “fusible.” When heated separate pieces of it can be joined into one. These and other qualities or “powers” to affect our senses, to affect other bodies, and to be affected by other bodies can be hidden from us on a first view and only discovered by long experience with the object. And we can never be sure that we have discovered all the powers that there are. This means that gold can be described, but it cannot be defined. We can list the simple ideas that we have so far discovered to arise when are affected by what we consider to be a piece of gold. But we can never be sure that we have come up with a complete list.

Something similar happens with ideas of reflection. We think there is something that produces the ideas of perceiving and remembering and feeling and willing that we discover when we reflect. We imagine others to also have these ideas of reflection and so to have something in them that produces their ideas. And we consider this thing to be better known by those who are more reflective, and perhaps not thoroughly known by anyone.

It is not always like this. Sometimes, we “close off” the list of simple ideas that we consider to go together in a compound. In these cases, we do not commit ourselves to the existence of any particular thing that brings about all the simple ideas. And we allow that there may be various, quite different things that could all produce that same complex of simple ideas. This is the characteristic of such complex ideas as “church,” “lie,” “hypocrite,” “drunk,” “triangle.” There may be no organization that brings about the exact complex of simple ideas that we consider to define a true “church.” Or there may be many more than one. There may be no perfect triangle. There certainly are many quite different objects that approximate a triangular shape.

This distinction between what I have called “open-ended” and “closed-off” complexes is the foundation for Locke’s distinction between substances and modes. An “open-ended” complex is the idea of a substance. There is some existing thing that it has to “live up to,” as it were. It is supposed to be produced by something that has an independent existence. A mode, in contrast, is something that we assume a prerogative to define. It may contain “less” than needs to be in a thing in order for it to exist. It may be “shared” or produced by many different things that do exist.

Though modes are often voluntarily invented by the mind, they can also be discovered in sense experience and reflection, just like substances. However, when we draw modes from sensory experience and reflection we still “close them off.” We take the collection of simple ideas that makes up the mode to be all we are after. We just want to specify a portion of the ideas the object brings about in us, without committing ourselves to having to later include other things that go into making the object what it is or ruling out the possibility that other, quite different objects might bring about the same collection of ideas in us. For example, rather than invent the complex mode, “hypocrite” on our own, we might come across someone who exhibits all the qualities that go into making a hypocrite, and this experience might inspire us to draw off and name that particular complex of simple ideas. Our idea will not include the person’s eye colour, though that was also experienced. And we will allow that others with differently coloured eyes might also be hypocrites. Though the complex is presented in experience we decide where to draw the bounds around it. Our experience of any one person is rich, and we include only some of that richness in the idea of a hypocrite. What we include and what we exclude is up to us.

Because we close off and define modes ourselves, we can teach them to others. This constitutes a third way, in addition to invention and experience, by means of which we can become acquainted with modes. They can be learned from definitions of words. Complex ideas, be they of simple or complex modes or of substances, are always given names, and these names are defined by giving a list of further names: the names of the simple ideas that go into the complex idea. Accordingly, rather than see various simple ideas combined in experience, or combine them ourselves in imagination, we can merely hear a name for a complex idea being defined, and doing that will lead us to think of the component simple ideas that go into the complex one.

To reiterate, though substances have names, definability is a special feature of modes. Substances can be described, by naming some of the simple ideas that they produce, but they cannot be exhaustively defined. This is because, as noted earlier, we can never be sure that we have enumerated all the simple ideas that go into making up a substance. We think of substances as having some “real constitution,” as Locke put it, that is, some arrangement of insensibly small shaped and moving parts that is responsible for giving the substance all the powers that it has. But we can never be sure that we have identified everything that this real constitution enables a substance to do — all the simple ideas it can bring about in us, or all the changes it can bring about in other bodies or undergo when in the presence of other bodies.

Like substances, simple ideas can be named, but since they have no parts, they cannot be defined. This is why, when discussing simple ideas, Locke frequently said that those who have had the requisite experiences would understand what he is talking about, but that nothing can be done for those who have not (other, perhaps, than to show them where to go to get the right experiences).

But modes can be defined, and this means that people who have never experienced a particular mode idea can nonetheless be given that idea by means of a definition, as long as they have experienced and learned the names for the simple ideas that go to make up the mode.

Modes. Locke distinguished between two kinds of modes. Simple modes are compounded from repetition of the same simple idea. The principal examples are distance, which is compounded to make distances of various lengths, distances of various lengths, which are compounded to make figures, space, duration, number, and infinity. In contrast, complex modes collecting different simple ideas together. They are exemplified by things like beauty, triangularity, health, drunkenness, theft, inquisition, and other features generally thought of as properties or accidents or actions or affections rather than as things.

Locke considered some of the more philosophically important complex modes in later chapters of the Essay. We will look at one of them, the idea of power in a later lecture. Here, I summarize some important anti-Cartesian points arising from his treatment of the simple modes, “space,” and “infinity.”

Locke considered the idea of distance to be a simple idea obtained from visual and tactual sensory experience. Colours, he noted, are all experienced as taking up some distance. So are the motions of our limbs. Since distance and colour, and distance and motion, are different simple ideas, they can readily be distinguished from one another, even though they are experienced together. And though our visual and tactual experiences present different specific distances to us, the imagination has a power to take any one of these ideas and repeat it, continually doubling it (or quadrupling it, or just adding it to itself, or whatever). It also has the power to divide it, continually halving it.

In the process of compounding or dividing distances, the imagination creates, or better discovers, something else as well: the idea of infinity. For Locke, the idea of infinity is a negative idea. It is the idea of a lack of finitude or of boundaries. When we take a distance and double it, we realize that nothing prevents us from doubling it again. As we keep doubling it, we keep encountering nothing that would prevent us from doubling it yet again. As this goes on and on, the distance we imagine becomes immense, but as immense as it gets, we think nothing would stop it from being twice as large again. This is the idea of in-finity, or a lack of finitude. Importantly, for Locke, this idea arises only when we repeat the same simple mode, as when we repeat distance, duration, or number to generate the idea of an unbounded distance, unbounded time, unbounded numerical sequence. The idea does not arise when we think of infinite perfection. That is because when we think of infinite perfection we do not just add the same quality to itself over and over. We add, or seek to add different perfections. But that requires that we be in possession of continually different perfections to add on top of one another — a rather more difficult task than just repeating the same idea over and over! — and one we cannot manage. Moreover, even when we just repeat the same idea over and over, we never arrive at an idea of the ultimate result of that operation. As Locke put it, we can only ever think of in-finite or unbounded space; we cannot think of “space infinite.” Similarly, we can only ever think of an unbounded numerical series, going on without reaching an end. We cannot think of an actually infinite quantity. If we could, would it be an even number or an odd one? The absurdity of the question betrays the absurdity of the enterprise.

The anti-Cartesian implications are obvious. We cannot form the sort of idea of God that Descartes so unreflectively thought we can: an idea that is the ens realissimum or sum of an infinity of different real or positive qualities. We cannot do this because we cannot conceive the sum of an infinite series, and because we can only continually augment the same quantity over and over, not an endless number of different qualities.

Descartes thought that the idea of God could only be formed by the understanding and not by the senses or the imagination. Locke’s reply was that an idea of the sort Descartes envisioned cannot be formed at all. We do in fact consider God to have all positive qualities. But we have no idea what this looks like. The best we can do is add together all the positive qualities we can think of and then imagine that there might be some more we cannot think of that might still be added. We can import the negative idea we have formed when thinking about space, time, and number and claim that there might be continually new perfections to add to God the way there are continually new distances to add to any finite space. But then all we are doing is cobbling together ideas obtained from sense and imagination to form what is more a recipe for forming an idea of God than the actual idea.

Locke had a further anti-Cartesian point to make. He noted that if we take various distances (e.g., various finite lines of different lengths) and pile them on top of one another as it were, and then consider the relations among the endpoints of these lines, we see that they form a figure. Pile different figures on top of one another and consider the relations between their extremities and we can form a “capacity” or “volume” or bounded space. And as distance can be augmented without end, so can space.

Importantly, this idea of unbounded space is a simple mode all on its own. It is not an idea of body. Our idea of body, Locke stressed, is the idea of something that takes up space, but also of something that is solid, that is, that resists the penetration of other bodies into the space it occupies. And because distances are always further divisible, a body that takes up space must be divisible into parts that, being solid, must also resist one another and so be separable from one another. After all, in virtue of their solidity, they are continually pushing away from one another even when hard up against one another. So body is solid and divisible extension. But space is not. Space can be divided into spaces, but those spaces cannot be separated from one another and moved around. Space is the network of places, and places don’t change place. They just are the ultimate places that abide where they are. Bodies change place and in doing so they move through space. This means that in addition to being indivisible space must be perfectly penetrable. It must allow bodies to coexist with it and in it. Space is not like the water around a fish, which moves to the side as the fish moves through it. It stays where it is and allows bodies to coexist in the same place with it. So another thing Descartes got wrong was the nature of space and body. Space is not just the extension of some body and body is not just space. Space is penetrable indivisible extension, and body is impenetrable, divisible extension.

Substance and substratum. The manner in which we form our complex ideas of substances has already been discussed. However, one important detail remains to be considered. According to Locke, we suppose our complex ideas of substances to be caused by individual objects that have various powers to affect our senses or our reflection with many different simple ideas at once. These individual objects are supposed to have some “real constitution” from which their various powers flow. This real constitution contains everything that is required to enable the substance to exist on its own, not just everything that is required to give it the powers to cause those ideas that we get when we encounter it.

But we have no idea of what this real constitution is.

Locke often speculated that the powers bodies have to cause ideas in us might arise from the size, shape, arrangement, and motion of solid parts too small for us to see, and that this arrangement of microscopic parts might be the “real constitution” of objects. But he also liked to tell a story about an Indian philosopher who supposed the universe to be supported on the back of an elephant that in turn stood on a tortoise who in turn stood on “I know not what.” Locke’s speculations about microscopic solid parts are not that different, and he knew it.

Here is one problem that Locke raised: Things that are solid resist being penetrated by what surrounds them. They push back against their surroundings. This means that any material that is composed of solid parts ought to fall apart into those parts, because the parts don’t naturally hang together but push back away from one another. The more parts the thing has, the more parts it should fall apart into. And if matter is infinitely divisible, which Locke thought it is, and occupies a void space that extends out beyond its limits and does nothing to contain it within bounds, then matter ought to just crumble or pulverize into a dust of particles so small as to be tantamount to nothing at all. It ought to effectively disappear.

The obvious consequence is that the material substances we think exist around us cannot just be composed of solid parts. There has to be something that makes those parts cohere, so that they don’t crumble into dust and nothingness under the influence of their mutual repulsion. But how are we to account for that? What makes particles cohere? It can’t be that they hook or thread into one another. That would beg the question. You need to already have coherent parts to make a hook or an eye or a thread.

And the problems do not end there. We might take a step back and ask what makes material parts resist penetration. It can’t just be that they are extended. Space is extended, but it does not resist penetration.

When you think about it, matter, or material substance is deeply perplexing. We speak of it as consisting of solid parts. But we have no idea what makes the parts solid, and we have no idea what makes the solid parts cohere. So when we talk about an arrangement of solid, shaped, and moving parts being the “real constitution” that accounts for the existence and the powers or secondary and tertiary qualities of a material substance, we are talking, like the Indian philosopher, about “something we know not what.”

According to Locke, this is the case with all of our complex ideas of substances, not just material but spiritual as well. There is something clear in these ideas, which is the collection of simple ideas that tend to go together and that are characteristic of the complex. But if we think that is all there is to it and close the collection off, we have a mode, not a substance. We have a collection of ideas that for all we know might be missing something essential for a thing to exist. We have a collection of ideas that for all we know might be brought about by quite different things. We only have the idea of a substance when we do not consider the collection closed, but instead consider it to be the product of some “thing we know not what” that exists independently of us and that has a collection of powers that we can never be sure we have fully catalogued or discovered. This additional idea of some ground or “substratum” for a collection of powers or qualities, both primary (like solidity and cohesion) and secondary or tertiary is a further ingredient in all our ideas of substances.

Many of Locke’s contemporaries, most notably Edward Stillingfleet, the Bishop of Worcester, were deeply disturbed by this account. They read Locke’s claims that substance itself is “something ... [we] know not what,” and something that we “have no distinct Idea of at all ... farther than of certain simple Ideas coexisting together” (Essay II.xxiii.2-3) as suggesting that there is no such thing as substance, and that when we talk about substance and substances we are using words without meaning.

In Stillingfleet’s eyes, Locke’s alleged scepticism about substance had a number of dangerous implications. Among the most serious was that it threatened the orthodox Christian doctrine of the Trinity. According to that doctrine, hammered out in the early centuries of the Christian church for reasons that need not be surveyed here, God is a union of three “persons” in one “substance.” In the early centuries of the Christian Church, this doctrine had been most famously questioned by Arius, from whose name the Arian heresy originates, and in Locke’s day Arianism had been revived by Faustus Socinius and other “Unitarians” in the extreme liberal wing of the Protestant movement. The Socinians viewed the belief in the divinity of Christ himself as nothing more than a “superstition” of the same sort as the generally reviled Catholic belief in Christ’s presence in the Eucharist. By questioning our knowledge of substance, and, in the minds of many, its existence, Locke appeared to be calling the doctrine of the Trinity into question, and opening the door to Unitarianism and other highly heterodox views of Christianity. If there is no substance, then the notion of three persons in one substance makes no sense. We are left with just three persons, and a choice between saying just one of the persons is God (hence, denying the divinity of Christ), or saying that all are (hence, denying monotheism). For most Protestant sects of the day (and the Church of England was no exception), this was viewed as tantamount to denying any recognizably “Christian” form of religion.

Locke had no wish to be branded heterodox, and in reply to Stillingfleet’s charge that he took “the being of substance to have no other foundation but the fancies of men” (Winkler, 343) he claimed that “it is of the idea alone I [spoke] there, and not of the being of substance” (Winkler, 343), and that “the being of substance is not shaken by what I have said: and if the idea of it should be, yet (the being of things depending not on our ideas) the being of substance would not be at all shaken by my saying, we had but an obscure imperfect idea of it” (Winkler, 343). Already in the Essay, he claimed, he had been at pains to observe not merely that there are psychological causes (various operations of the mind) inducing us to form the idea of substance, but also that there are solid rational grounds for affirming the being of substance itself.

Particular Substances. In addition to forming the idea of substance or substratum in general, we form ideas of particular substances. We arrive at these ideas through observing that different animals, minerals, vegetables and minds are characterized by different collections of simple ideas, and so are supposed to have different primary qualities and powers. Often, the bundle of simple ideas characteristic of a particular animal, mineral, vegetable, or mind will evolve and change over time, implying an evolution in the primary qualities and powers of the thing. Our notions of particular substances are ideas of something that gives rise to just these qualities and no others, and that is responsible for their evolving in just a certain way over time. Again, we have no idea of specifically what is responsible. We lack microscopical eyes and so cannot discern the corpuscular constitution that is responsible for the observed qualities and ideas we associate with substances. And even were we possessed of microscopical eyes, they would only stave off our ignorance for one step, since we would still have no vision of what it is in each small part that enables it to cohere with the surrounding parts while at the same time resisting penetration by them. We merely indicate or designate this unknown something by using names like substance, or, more commonly in this context, essence.

This ignorance of an underlying “real constitution” entails that our ideas of specific substances can vary, relative to the person who has them. Some people, who are more attentive and observant, will see more substances in the world than others. Whereas one person will refer to everything that is ponderous, rigid, strongly resistant to division, and brittle as a stone, another person will discriminate between stones, which are not malleable, and metals, which are. Yet another person will distinguish different kinds of metals from one another on the basis of things like their colour and their mass, and so separate yellow, heavy metals, like gold, from lighter, dark metals, like iron.

Different people may also have different ideas of substances even though they use the same name for these ideas. For a child, and for most people in the street, gold is any yellow, heavy metal. Brass could be gold for all they know. A metallurgist has a more detailed concept of what gold is. But even the metallurgist’s concept of gold consists of no more than (a somewhat more expanded) list of simple ideas and complex modes (most notably powers): yellow, heavy, malleable, fixed, fusible, and so on. Neither the metallurgist nor the person in the street has any concept of what it is in the substance that makes gold express all of these ideas. Their concept just reduces to a more or less extensive collection of simple ideas.

Aristotle had maintained that to know a substance is to know the “essential form” that makes it express all the qualities that it has. But Locke said that this sort of knowledge, knowledge of the real essences that make substances what they are, is beyond us, and that all even the most sophisticated person can ever hope to know is the collection of ideas the thing brings about in us. With more care and attention, we can expand upon the list of ideas the thing characteristically causes, and we might be able to explain some of these ideas, like those of colours or temperatures, as effects of others, like the shape, hardness, and motion of insensibly small parts, but, while that enterprise is valuable insofar as it serves to uncover common causes for a variety of different effects, it can only push our ignorance back a step, to the causes of the unity and endurance of the primary qualities of things.

The Substance of the Soul. This helps to explain why Locke’s account of substance continued to get him in trouble, despite his claim to have never wanted to cast doubt on the existence of substance or substances. Aside from its implications for the doctrine of the Trinity, Locke’s views on substance were taken to have another dangerous implication, and this was not one that he could deny, but was actually concerned to assert. The implication concerns the substance of the soul.

At Essay II.xxiii.5 Locke wrote that “The same happens concerning the Operations of the Mind, viz. Thinking, Reasoning, Fearing, etc. which we concluding not to subsist of themselves, . . . are apt to think . . . the Actions of some . . . [substratum], which we call Spirit.” Just as we suppose that those external sensations that we constantly observe to go together must be caused by some material substratum, which supports the qualities corresponding to them, so we suppose that our internal sensations, of thinking, perceiving, willing and the like, are all caused by some spiritual substratum.

Our tendency is to suppose that it must be a different substratum. We think this because we have no idea how a thing of the sort we suppose to cause our ideas of sensation be could be responsible for such different ideas as those of reflection. Locke noted that our sensory ideas of material things are principally characterized by two features, a cohesion of solid parts, and a capacity, resulting from solidity, to communicate motion on collision or what Locke called “impulse.” Our reflective ideas of spiritual things are principally characterized by two quite different eatures, a capacity to form ideas (in some cases as a conjectural consequence of sensory “impulse”), and a capacity to initiate or originate motion through a bare preference or thought, which we call willing or volition.

But while the ideas that we take to be characteristic of material and spiritual substances are very different, they are not clearly incompatible. One and the same substratum could conceivably be responsible for bringing about both sets of ideas. In other words, matter might be capable of thought.

This is not a consequence that Locke trumpeted in Essay II.xxiii, though he did slip it in later, at Essay IV.iii.6. In the earlier Essay II.xxiii, Locke repeatedly declared that spiritual substance is as clear and as intelligible as material substance, so that we have no more reason to deny the one than the other. This sounds as though it were directed against Hobbes’s claim that spiritual substance is virtually a contradiction in terms. But on closer inspection it turns out that the reason Locke thought that our notion of spiritual substance is on a par with our notion of material substance is that we have no more of an idea of the substratum enables solid parts to cohere than we do of the substratum that enables a thought to initiate a motion of the limbs of the body, and no more of an idea of the substratum that allows impacting bodies to push one another away rather than allow themselves to be penetrated than we do of the substratum that produces perceptions as a consequence of impulse. We have as clear a notion of the [substratum] of Spirit, as we have of Body,” Locke declared, which is to say that we have no idea of either sort of substance.

Descartes had claimed that nothing is more clear and certain than that I exist. But Locke, looking at Descartes’s result, was only able to find it to be clear and certain that ideas of reflection exist — that there is thinking, willing, perceiving, remembering, and so on. He allowed that these things can no more exist on their own than can colours, extension or solidity. But since all that we know are the qualities that inhere in these substances and not the substances themselves, we are in no position to make any claims about the ultimate, inner nature of matter or spirit. In particular, and as Locke pointed out in Essay, IV.iii.6, we cannot be sure whether the substance in which our ideas of thought and volition inhere is distinct from the substance in which our ideas of solidity and impulse inhere. As a consequence, and notwithstanding the show made in Essay II.xxiii of rejecting materialism, it appeared to many that, like Hobbes before him, Locke meant to suggest that the soul is material and that there is no afterlife. To the degree that these implications were less explicit in Locke’s work than in Hobbes’s, that only made his work all that much more insidiously dangerous.

ESSAY QUESTIONS AND RESEARCH PROJECTS

1. Do a study of the correspondence between Locke and Stillingfleet on the topic of substance. Outline the course of the correspondence and assess the quality of the arguments on either side. Do a review of what other English critics of Locke’s views on substance were saying at this time.

2. In his exchanges with Stillingfleet (see Winkler, 341-45) Locke denied ever wanting to suggest that there is no such thing as substance or even ever wanting to suggest that our idea of substance arises simply from a sort of verbal illusion. He claimed instead that the necessity of the existence of substance, and the consequent legitimacy of our idea, is proven by the fact that none of our simple ideas, including those of extension and solidity, can exist on their own. As he put it at II.xxiii.4, “because we cannot conceive, how [the complication or collection of those several simple ideas of sensible qualities that we find united in things such as those we call horse or stone] should subsist alone, nor in one another, we suppose them existing in, and supported by some common subject.” Was Locke right about this or might a critic object that a simple idea could very well exist on its own or that two simple ideas might mutually support one another’s existence without needing to inhere in some substance? If he was not right, is there some other good reason for supposing that substance must exist? In answering these questions, consult the views expressed by Hume in Book I, Part iv, Sections 2-4 of his Treatise of human nature.