Species and Essence in Locke’s Essay III.vi

In book three, chapter six of his Essay, Locke discusses the relationship between species and essence in the context of a broader discussion of the names of ideas of substances. In the sixth section of the chapter, Locke appears to claim that real essences are properties of species or sorts, rather than individuals. Interpreting the passage in this way poses two related problems for Locke’s theory. First, if Locke is claiming that the real essence, rather than the nominal essence, is closely related to the species, then this is a direct contradiction of what Locke says about which type of essence is possessed by species elsewhere in the essay. Second, given Locke’s criteria for the demarcation of real from nominal essences earlier in the essay, it is difficult to see how a claim that substantial species have real essences is even comprehensible. I want to consider these problems in more detail and offer an alternative interpretation of the passage in question that attempts to avoid attributing contradictory or unintelligible views to Locke.

The passage at issue is found in III.vi.6. Here Locke is discussing the difference between real and nominal essence in substances, and after defining real essence using his standard definition (the real constitution of a thing which is the foundation of its properties), Locke proceeds with the odd claim that essence “even in this sense, relates to a Sort, and supposes a Species: For being that real Constitution, on which the Properties depend, it necessarily supposes a sort of Things, Properties belonging only to Species, and not to Individuals.” An individual parcel of matter has no essential properties; it is just the arrangement of minute particles and their motion, which can change or be changed by its interactions with other bodies in the world. Therefore, according to Locke, any properties referred to as essential must be so only as part of a species concept, since it is only our general ideas which possess the requisite immutability to have essential properties. A “face value” interpretation of this passage leads us to the conclusion that Locke holds that species, not individuals, possess real essences.

The first problem with the face value interpretation is that the claim that species have real, instead of nominal essences, is in direct contradiction with things Locke says elsewhere in the Essay. For example, in III.iii.11-12 Locke concludes that “General and Universal do not belong to the real existence of Things” but are inventions of the mind for use in organizing perception and “concern signs only”. A general term signifies a class of a sort of thing by “being a sign of an abstract Idea in the mind”; under which particulars are classed which “agree” with the abstract idea. Species are on this account nothing but abstract ideas. Species do not exist in the world. To be a member of a species is nothing more than to have a right to be called the name of that species, a right which is derived from agreement with the abstract idea. This is the type of idea that Locke speaks about a few sections later in III.iii.15-16 when discussing nominal essence, which instead of referring to the real, hidden constitution of things is applied to the “artificial Constitution of Genus and Species.” This is highly suggestive that Locke does not consider species of substances to have real essences (i.e., real constitutions) but rather artificial constitutions and nominal essences.

In addition to these passages suggesting that species have only nominal, and not real, essences, there are passages that indicate that only the nominal essence is used in the formation of species concepts. III.vi.7-8 indicates that the nominal essence is at work in the classification of species. It is impossible to arrange or classify substances by reference to their real essences (which are unknown), so the only means by which to erect species boundaries is by reference to their nominal essences. We class as the same species different particulars whose properties agree with the abstract idea that is signified by the name of the species. Locke also cites as additional evidence that species classifications are based on nominal essences rather than real essences the fact that two objects of the same species can differ from each other in their inessential characters as much as they might differ from another object from another species, without disturbing that classification, even though all properties flow from the same real constitution. A similar point is made by Locke at III.iii.17. So if we are to keep Locke from contradicting himself and also interpret our original passage as indicating that Locke holds that species, not individuals possess real essences, we will owe an explanation as to why species are listed as just the types of things which have nominal essences instead of real essences in the case of substances as well as why only the nominal essence would be useful in species classification.

In addition to the problem of keeping Locke from contradicting himself, there is the problem of making sense of what a real essence of species could possibly be, given Locke’s discussion of the differences between real and nominal essences. For Locke, real essences are related to the real constitutions of things, which are unknown in substances (III.iii.15). In substances, those essences are material; they are the physical arrangements of the parts of substances, from which their properties flow. The conjunction of properties which makes up our idea of a species (i.e., its nominal essence) is distinct from the real essence in substances. Locke claims that the essence of a species is nothing but the abstract idea to which its name is annexed (III.iii.12; III.vi.2) and that no one would assert that the abstract, complex idea of a species is the real essence and source of the properties we observe (III.vi.3).

But if a species is an abstract idea and possesses a nominal essence, what would it mean for the species to have a real essence? In other words, how can an abstract idea have a hidden internal constitution from which the properties of an object flow? Since our complex, abstract ideas are constructs of the mind, Locke believes that we have full access to them—nothing is hidden from us. Also, nothing in Locke indicates he believes species to be material things, and his discussion of the real essences of substances indicates they are material in nature. To attribute real essence to species we would need to resolve this difficulty. In addition, in his discussion of real essences, Locke makes use of causal language to indicate that the real essence is the source of the properties by which our species concepts are formed. Since the species concept (the abstract idea we have of a species) is the nominal essence of a species, by making the species the seat of the real essence Locke would then ensure that the nominal essence would be identical to the real essence in substances, something which Locke explicitly denies (III.iii.18). These considerations ought to make us consider that perhaps reading our original passage as attributing real essences to species is incorrect.

But if Locke is not claiming that species have real essences, what is going on in our original passage? I believe it is possible to interpret III.vi.6 in such a way as to minimize the complications sketched above and still remain faithful to the text and its context. The sections immediately preceding and following the passage in question are occupied with Locke’s attempt to demonstrate that individual parcels of matter do not have essential properties. For example, a piece of iron must possess the ability to be pulled by a magnet if it is to be iron, but there is no necessity for any parcel of matter to be magnetic; in other words, Locke is claiming that it is possible for bodies to have properties other than the ones they have (III.vi.4-5). The properties that individual objects have are then used by the mind to classify objects into kinds and assign nominal essences. The real essences of objects are not made use of in the assignment of species designations to individuals (III.vi.7-8). Essentially, the context in which Locke links species with real essences is an epistemic, rather than a metaphysical one. He is not here claiming that there are real species which exist independently of things that fall under them or of the minds which construct them, but rather that the properties which are referred to as essential to a particular thing are only intelligibly called essences in terms of the sort or species of thing they are taken to be an instance of. He is claiming that the only intelligible way to speak of properties as essential is to do so in the context of species concepts.

I do still want to affirm, however, that Locke intends to tie real essences to our species concepts in this passage. Locke believes that properties which manifest themselves when we observe a substance are caused by the real essence of the substance. The ideas we have of these properties are then combined into the complex idea that forms the nominal essence of the species of the substance; this is the link whereby the real essence is connected to the species. Locke says as much at the end of the section: “as to the real Essences of Substances, we only suppose their Being, without precisely knowing what they are: But that which annexes them still to the Species, is the nominal Essence, of which they are the supposed foundation and cause” (III.vi.6). Basically, species have real essences, but only mediately, through their possession of the nominal essence which is composed of ideas which are caused by the real essences.

This reading of Locke in III.vi.6 allows us to affirm that Locke does tie real essence to species in a deliberate way, as a face value reading indicates. However, by interpreting the claim as one which ties real essence to species through our epistemic or classification practices rather than as positing a real essence directly possessed by a species, we can read Locke without making him contradict himself or claim something incomprehensible.

Descartes' Argument from Conceptual Content

Descartes offers three different arguments for the existence of God over the course of the Meditations. The first is an argument for the necessity of God's existence based on the nature of ideas and the content of our concept of God.

His demonstration of God’s existence begins with an analysis of ideas. According to Descartes, it is in the nature of ideas that they receive whatever "objective reality" they possess from something with as much or more objective reality. Descartes argument is this: if an idea contains something that is not in its cause, then it has come from nothing. But nothing comes from nothing. Therefore, the ideas I have cannot contain more perfection (or reality) than their causes. Descartes makes an analogy to pictures for support—a picture can fall short of perfect resemblance to its subject, but it makes no sense to claim that a picture exceeds the reality or perfection of that which it represents (CSM II 27-9).

What exactly he means by objective reality is a little difficult to pin down, and does not become significantly clearer even when he is pressed on the issue in the Objections and Replies that follow the Meditations. As far as I can tell, Descartes seems to subscribe to the notion that there are grades of being; substances have more reality than modes, for instance. This much was a fairly common notion at the time. But what I'm not sure was as common or uncontroversial is his claim that our ideas of substances have more reality than our ideas of modes, and this difference in reality is a causal consequence of the difference in reality of the entities the ideas represent. This undefended claim is necessary for his argument to get off the ground.

So Descartes concludes that any idea he has that has more objective perfection than he possesses cannot have originated within him. Ideas of material things contain nothing so great that they could not originate within him, however. Because so few of our ideas of corporeal things are perceived clearly and distinctly it is difficult for us to judge whether they are representations of real or unreal things, and so it is difficult to say whether they are the true cause of our ideas of them. Even those elements that are clearly and distinctly perceived in our ideas of objects could be supplied by our own minds (CSM II 29-31).

It is only when he comes to the idea of God that Descartes finds an idea that possesses a degree of objective perfection such that it couldn’t have come from within himself. All of the perfections of God that are present in objective reality within the idea of God must have been produced by a cause with as much perfection. It couldn’t be an extension of our idea of finite substance, because there is more reality in an idea of an infinite substance than in an idea of a finite one, and as finite substances we could not be the source of an idea of an infinite substance. Even though the idea we have of God is inadequate, the degree of perfection it possesses is sufficient for me to know I am not the source of it (CSM II 31-2).

There are several points at which this argument is problematic. First, it's not at all clear that even if there exist degrees of reality in the world that this continuum of existence is reflected in our thoughts. What reason do we have for saying that our idea of a unicorn is less real than our idea of a horse? Clearly a horse is real and a unicorn is not, but what sense does it make to say that the ideas we have of them possess different levels of reality? Descartes simply stipulates this continuum of ideas and doesn't offer us any reason why we should accept it.

Second, even if we grant that ideas do display this continuum of being, there is no indication that this variability in reality is isomorphic with the variability of the reality of the entities the ideas represent. He argues only that there must be some cause of the contents of our ideas, but the move to the notion that the objective reality of the contents of our concepts parallels the objective reality of their objects is a sleight of hand. It's certainly conceivable that the contents of our ideas (and thus the differing objective reality) could have come from some other cause than the object they represent.

These two considerations are sufficient to block the argument, but I also want to look more closely at his contention that the idea of God is something that couldn't be a human construction, because this notion recurs in theological arguments from time to time in one form or another. Descartes bases his claim that our idea of God cannot be a construction on the claim that the idea of an infinite substance cannot be an extension of our idea of finite substance; that is, there is no mental operation available to us to build an idea of infinite substance from our ideas of finite substances. In reality however, it seems eminently plausible that just such an operation is available to us.

Take as an example the idea of numerical infinity; we certainly don't have an idea of numerical infinity on the basis of having ever experienced infinite numbers, but we can construct an idea of numerical infinity by repeating a mathematical operation on a number (addition) and recognizing that there is, in principle, no limitation on applying indefinitely. One plus one is two, plus one is three, plus one is four, and so on. We can have an idea that there is no upper limit on numbers because we see that addition can continue indefinitely.

Why couldn't the infinite properties of God be constructions in exactly this way? Our idea of his infinite goodness can be an extension of the notions of goodness we have from our experiences in the world. Similarly with all the other properties of God; the infinity, power, knowledge etc. that we attribute to him could simply be exaggerations of things we experience in the world. Descartes admitted that the idea of God we have is inadequate but claimed that degree perfection they possess shows that cannot be human construction. This however, does not seem to be the case.

Cottingham, J. G., Stoothoff, R., and Murdoch, D. (eds), The Philosophical Writings of Descartes, 2 vols. Cambridge University Press, 1985.

Evaluating the First Enquiry critique of traditional religion

I've summarized the two sections that comprise the two halves of the critique of traditional religion contained in Hume's First Enquiry here and here. Now I want to take a look at how the two arguments complement each other and evaluate how good a critique they make.

Although he is not explicit in this, I take it that Sections X and XI of the First Enquiry are intended by Hume to jointly show that neither the miraculous events of revealed religion nor the conclusions of natural theology can serve the purpose of acting as a rational foundation for religious belief. Hume leaves it to the reader to evaluate whether religious belief is rational without these supports, but the implication is pretty clear that he thinks it is not.

As I see it, there are three main approaches to establishing the foundations of religious belief in the history of philosophical theology. First, there is the a priori approach, exemplified by the sorts of arguments that occupied mediaeval theologians. The various formulations of the ontological argument, the first cause argument, etc. are ways of attempting to establish the existence of God and determine his properties through an analysis of the contents of our concepts and by applying deductive logic once those concepts are clarified. Second, there is revealed religion, which calls on miracle accounts, authority, tradition, scripture, and revelation to provide the epistemic justification for religious belief. Third, there are a posteriori approaches to religion exemplified in natural theology. This approach looks at the way the world is and argues that the existence of God is a necessary component of any adequate explanation of the world.

Hume's critique is targeted at the second and third approaches. His critique of revealed religion is primarily occupied with the lack of foundation of miracle accounts, but the argument is easily extended to all forms of justification of revealed religion. There is no logically sound reason why we should believe anything on the basis of authority, scripture, tradition, or revelation. There is simply no logical connection between the speaker of a proposition and its truth value.

Our confidence in each of these bases must then rely in their perceived reliability. But experience is the only way to determine what is reliable, and so the content of a claim made in scripture or from the pulpit has to be judged according to the likelihood criteria by which all other claims about matters of fact are judged. And in the case of vast swaths of scripture, tradition, etc. the overwhelming evidence is that the way religion describes how the world is (with miracles, angels, talking donkeys, resurrections, etc.) is far different than  our normal sensory or scientific experience of the world. This being the case, we ought to apportion our beliefs to the evidence and reject revealed religion.

Hume's critique here is devastating to the method of justification of revealed religion. An advocate of revealed religion will have to offer a plausible reason to think that authority, etc. are generally trustworthy that does not call on reliability, because as Hume has shown, the probability (and thus general reliability) of scientific accounts of the world that contradict religion is far greater than the probability that the miraculous events that pepper scripture and tradition actually occurred. This reason won't be able to point out a necessary connection between the source of information and its truth value because no such connection exists. And it won't be able to claim that we can trust revelation, authority, or scripture as true or miracle accounts as likely because of the truthfulness or power of the deity, because the existence of this deity or the truth of religion is supposedly justified by these things. Invoking God to buttress the veracity of the scripture (or authority, etc.) which is used as a reason for positing God's existence is as straightforward a circularity as you could ask for.

The reach of his critique of the Design Argument is much more limited, however. A posteriori proofs for the existence of God are essentially inferences to the best explanation, and at the point at which Hume was writing in the mid 18th C., there was not much in the way of scientific theory that could conclusively argue against a divine creator being a candidate for the best explanation for the existence of the universe and the order that we see in it. Newton's universe was a static place with fixed laws and no discernible origin; it is not until the development of modern cosmological theory that anything approaching an understanding of the beginnings of the universe was developed. Similarly, Darwin's extraordinary achievement of detailing a natural mechanism to explain adaptation and order in the biological world was still a century away. So, Hume was unable to fully refute the Design Argument's claim to have established the likelihood of a deity.

What Hume's argument did accomplish, though, is still significant. By correctly identifying the Design Argument as an argument from effect to cause he was able to show just how little advocates of that argument can hope to get from it. All it warrants is the inference to some being or entity of we know not what sort with we know not what properties that is sufficient somehow to bring about the existence of the universe in some fashion. Not exactly the anthropomorphic God of traditional religion. Nothing more can be concluded because for the other attributes traditionally attributed to God (omniscience, omnipotence, goodness) there is scant evidence in the world we see. The Design Argument gives us none of these properties. And, having blocked the methods of revealed religion, Hume has also blocked one avenue of supplementing the minimal conclusions of the Design Argument to get something approximating Christian dogma.

Hume's critique does not address the a priori method of establishing the existence of God, however. My supposition is that his Empiricist worldview would have led him to simply dismiss any a priori arguments attempting to establish the existence of God, or for that matter, any matter of fact. He probably was right to do so, but defending that position is a task for another day.