Existence and the Cogito
The Cogito strikes most people as intuitively valid, but it has been trenchantly criticized. How exactly the inference is supposed to work still excites controversy. Here I will consider a line of objection that I have not seen pressed before. The natural way to interpret the inference is that it moves from a premise about instantiation to a conclusion about existence: I know with certainty that I instantiate the property of thinking, so I must exist as the subject of this property. We might expand the argument as follows: “I have the property of thinking; if something has a property, that thing must exist; therefore I exist”. My thoughts exist (as I know with certainty), and they must be instantiated in some object; this object is not identical to my thoughts; so we can infer that there exists an object (viz. myself) that is not identical to my thoughts. Thus we can move nontrivially from the existence of thinking to the existence of a thing that thinks. But consider the analogous argument concerning unicorns: “Unicorns are horses with one horn, so unicorns instantiate the property of having a horn; but there has to be an object that instantiates this property; therefore unicorns exist.” Or: “Santa Claus has a beard, so he instantiates the property of having a beard; but then he must be an object that instantiates a property; therefore Santa Claus exists”. The premises seem true but the conclusion is false, so the argument must be invalid—but where does it go wrong? Meinong would give the following answer: it does not follow from the fact that an object instantiates a property that the object exists—it might only subsist. In more recent terminology, these objects might be merely “intentional objects” not real existent objects; and so instantiation does not imply existence on the part of the instantiating object. Applying this point to the Cogito, what is to rule out the possibility that the self is a merely intentional object that instantiates the property of thinking but does not exist? We can see that objects are able instantiate properties without thereby existing, so why can’t the self be one of those? To be sure, the properties exist—they are real entities all right—but it doesn’t follow that anything that instantiates them is itself real. Fictional objects are a counterexample: the property of being a detective is a real property, but the fact that Sherlock Holmes is a detective doesn’t make him real. Likewise, thinking is a real property that things can have, but it doesn’t follow that anything that instantiates this property is itself real—after all, Holmes also thinks. Maybe the self is like Holmes.
How might we respond to this objection? One possibility would be to appeal to the certainty of the premise that I think, holding that this is what sets the Cogito apart. But am I not also certain that unicorns have one horn, that Santa Claus has a beard, and that Holmes is a detective? The fact that an object certainly instantiates a property does not automatically confer existence on that object (it is certain that the Golden Mountain is a mountain). Another possible way out would be to question the whole ontology of subsistent or intentional objects, insisting that there are no objects but existent ones. This flies in the face of the seemingly obvious fact that some things don’t exist and yet have properties; but also, from the point of view of the Cogito, it gives up the certainty of the inference—for now we have to accept that the validity of the Cogito depends on the rejection of Meinongian metaphysics. Maybe we should, maybe we shouldn’t, but we don’t want the fate of the Cogito to be tied to that metaphysical issue. No one hearing the Cogito for the first time thinks, “Well, it depends on your view of Meinong”. Descartes surely did not take a stand against Meinong-style ontology when he enunciated the Cogito. The validity of the argument should not depend on whether or not you entertain Meinongian predilections. It isn’t as if those with such predilections are prohibited from accepting the Cogito; at any rate, that’s not the way the question presents itself.
A third suggestion is that there is an asymmetry between unicorns (etc.) and thinking selves, namely that you can hallucinate unicorns but you can’t hallucinate thinking selves. Thus it can seem to you as if there is a unicorn in front of you without there being one, but you can’t hallucinate having thoughts without actually having them. That asymmetry must be conceded—beliefs in unicorns are not epistemically necessary but beliefs in thoughts are—but it doesn’t help to salvage the argument: for all we get from this is that the existence of thoughtsis certain, not that the existence of thinking selves is. True, we can be certain that thoughts exist, but we could still be in error about the existence of a self that has them. There might be nothing except thoughts in the vicinity. We might be under an illusion about the self, as we might be under an illusion about unicorns. We might be misinterpreting a collection of thoughts as a self that has them. Compare seeing a swarm of bees in the distance and mistakenly thinking there is a single big organism there. Maybe we hallucinate a unitary self when we introspectively encounter a swarm of thoughts. Who knows what might be going on? We can’t hallucinate the thoughts, but we could be under an illusion about what they signify, i.e. an underlying unitary self. Similarly, when we hallucinate a unicorn we are not hallucinating its component properties—they are real enough qua properties (though their present instantiation is illusory). Anyway, even if it is somehow impossible to hallucinate a self, why should the existence of a self be entailed by the existence of individual thoughts? We still haven’t justified the step from the existence of thoughts to the existence of a thing that has them (the Gassendi-Lichtenberg objection).
Fourth, we might hope to find something in the specific nature of thought that guarantees an existent thinker, where this something is not present for properties in general. Maybe having a single horn doesn’t prove the existence of what has the horn, but thought might be such as to necessitate an underlying existent thinker. This would be the analogue of the ontological argument: most properties indeed fail to guarantee existence, but the property of total perfection does guarantee it, because of its specific nature. Instantiation by that property entails the existence of the instantiating object (according to the ontological argument). There has been a strong intuition (notably voiced by Frege) that mental states necessarily require a bearer—something that has them, a subject. But it is far from clear how this can help the Cogito: Meinong could agree with this point while insisting that the bearer is a merely subsistent entity. Fictional mental states logically require a bearer too, viz. a fictional character, but they lack existence. The notion of a subject of predication—an object of instantiation—is too weak to deliver the conclusion of the Cogito: we might be predicating thought of a non-existent object. But also: does the intuition hold for all kinds of mental states or only thoughts? And does it apply to unconscious mental states as well as conscious ones? Is it true of the bodily sensations of jellyfish or worms? And is the point any different from the claim that any kind of state needs something for it to be a state of, including the state of being electrically charged or the state of the weather? We really need an argument, analogous to the ontological argument, showing that thinking inherently and uniquely calls for an existent subject that can be the reference of “I”, but what this argument might be remains elusive. Could it be that the capacity to think requires the capacity for the self-attribution of thoughts, and hence for a self? But what could establish that, and how would it guarantee the reality of the self in question? Descartes never argued anything of the kind, and it would certainly undermine his claim that the Cogito is primitively compelling. So there is nothing comparable to the ontological argument showing that it is in the nature of thought to bring with it an existent bearer, let alone one with the characteristics of the self as normally understood. 
But perhaps there is an intuition lurking in this unsuccessful argument that might have more cogency: namely that there is a contradiction in the idea of existent thoughts occurring in a non-existent object. Fictional thoughts can occur in a fictional object, but non-fictional thoughts require a non-fictional object. Thoughts are particulars not universals (token not types) and existent particulars need existent objects to inhere in. Properties can exist and be properties of non-existent objects, but events and processes can’t both exist and also inhere in non-existent objects. What would it mean for Sherlock Holmes the fictional character to have an existent real thought? Wouldn’t that make him real? So there is a metaphysical assumption at the heart of the Cogito: those thoughts whose existence is evident to us must exist in a being that is itself existent, since real events need real objects as bearer. Real mental particulars need real mental substances to inhere in—they can’t exist in an unreal substance. In Meinong’s language, existent events cannot inhere in merely subsistent objects. If there is real thinking going on, then this requires a real entity to do the thinking; and we know for sure that real thinking is going on—hence we know for sure that we exist. If the thinking was fictional, the subject of it would or might be fictional too; but granted that the thinking is not fictional, neither can he thinker be. Thus I know that I am not a character in fiction (or a “logical fiction” or an hallucination). Compare the bodily counterpart to the Cogito: “I have a body, therefore I exist”. We could not object to this that the premise could be true and the conclusion false, because the body, not being fictional, cannot be had by something fictional: something must non-fictionally exist if my body non-fictionally exists (whether it is the reference of “I” is a further question). We can infer from the existence of the body that something exists. To be more precise, if I know that I have bodily states, then I know that something exists in which those states occur—for example, if I digest there must exist something that digests. The inference is solid because it is compelling to claim that physical states require a physical bearer—a physical thing that has them. If I know there are physical states, then I can deduce that there are physical objects, because states must be states of something. And it would be absurd to suggest that existent physical states could exist in a non-existent object—a merely intentional object. If Holmes is in real physical states, then he must be real himself—fictional characters can’t have real indigestion! The difference from the classic Cogito is just that the premise here is not certain (not an epistemic necessity): I don’t know for certain that I am in physical states or even that I have a body. So this is no use for Descartes’s purposes, though the connection between premise and conclusion is the same in both cases, viz. a metaphysical principle precluding unreal bearers of real states. As we might put it: we can’t mix the existent with the subsistent, the real with the imaginary, the factual with the fictional.
Where does this leave the Cogito? It allows it to struggle on, to retain a semblance of cogency, but it leaves it vulnerable to skeptical doubt. Descartes was working with a scholastic metaphysics of substance and accident—his evil demon was not supposed to call that into question. Against this background the Cogito is relatively smooth sailing. But a dogged opponent might protest that this metaphysics is not immune to doubt, and if it is doubted the Cogito will not go through. Why should we accept that there are substances at all, material or immaterial—why not make do with an ontology of states, events, and processes? Later philosophers indeed did advocate such a low-calorie ontology (e.g. Russell) and so there is no substance in the world for thoughts to inhere in anyway. Thoughts may form sets or aggregates, according to this point of view, thereby gaining a sort of collective unity, but they don’t inhere in substances. So there is no valid metaphysical principle licensing the move from the existence of states to the existence of substances that support them. That may be wrong as a piece of metaphysics, but in the context of the Cogito it would need to be addressed.
More subtly, however, there is this problem: the prima facie persuasiveness of the Cogito seems not to be hostage to the kind of principle I have invoked to bolster it. Is this what someone is thinking who accepts the Cogito? Possibly, but it would have to be in some subliminal or tacit manner, since the requisite principle is hardly laid bare in the usual presentations of the Cogito. It takes work to come up with it and it is not entirely self-evident, even if you accept it. So it is not clear it can explain the felt cogency of the Cogito; indeed, it renders it much more wobbly than we might initially have supposed. Once it is fully articulated in this way its appearance of self-evidence starts to fade, and yet it is routinely hailed as the surest of philosophical theses. The resourceful Meinongian has produced a new threat to the Cogito, and the suggested repair to the argument lacks transparent cogency, even if it is ultimately correct as a piece of metaphysics. So we are left in a rather unsatisfactory position: the argument is not clearly valid but not clearly invalid either. I would say that it can be salvaged more effectively than might have seemed possible once the Meinongian objection has been formulated; for that objection looks formidable at first sight and it takes some ingenuity to forestall it. Hume’s kind of critique of the self, which takes the self as a type of fiction (at least on some interpretations of Hume), was evidently alien to Descartes and quite inimical to the Cogito(we can’t deduce the existence of a substantial self merely from the existence of ideas encountered internally). And yet it is hard to deny that the Cogito has all the appearance of self-evidence, whatever its final analysis may turn out to be.  This philosophical gem thus remains as tantalizing as ever.
 What we are entitled to assert on the basis of the Cogito is that the certain existence of thoughts proves the certain existence of something that has them. That is, thoughts need a bearer because they must be instantiated by something other than themselves; but this bearer could be anything, even a non-existent fictional entity. Call this the weak Cogito: it doesn’t deliver a substantial self with the intuitive characteristics of the self, and is quite compatible with a Humean view of the self, but at least it shows that there is something that can’t be doubted (in addition to the existence of thoughts themselves). If we employ a particular quantifier shorn of existential import, we can say that the weak Cogito allows us to assert the following proposition: “I think, therefore there is something that thinks”—where the quantifier can range over even purely intentional objects that lack existence, or any kind of existent object, physical or non-physical. The strong Cogito, by contrast, asserts that we can prove that a substantial existing conscious self underlies the existence of thoughts (there is also room for intermediate strengths).