Do I Know That I Exist?

Do I Know That I Exist?

I am going to argue (a) that the Cogito cannot prove that I exist but (b) that it can prove that various other things exist. This is ironic given that it is commonly supposed that the Cogito can establish the existence of the self (person, subject) but that only the self’s existence permits of such a demonstration. Both these points are actually quite easy to establish, as it turns out. In order to know whether the Cogito can prove the existence of the self, we need to know what the self is. So: what am I? That is a philosophical question—a question of metaphysics—and there are several answers to it that have been proposed. These are: the self is an animal body; the self is a composite of a body and a mind; the self is just a mind (“conscious subject”) and nothing more; the self is a primitive entity that can be described both mentally and physically. It is clear that three of these views will not permit the deduction of the self from the premise “I think”. For we cannot deduce from that premise that a body exists: that is subject to Cartesian doubt and is not entailed by the mere existence of thought (but see below). Nor did Descartes suppose otherwise: he didn’t think he could deduce the existence of any extended substance, such as a human body, from the premise that he thinks. So, if any of these bodily views is correct, the Cogito is powerless to demonstrate the existence of the self so understood. No, what Descartes supposed is that the Cogito can prove the existence of the self as a purely mental thing (a “res cogitans”). So, what is this purely mental self? Clearly, it is the subject of mental attributes: not just the attribute of thinking but also of desiring, intending, imagining, feeling, believing, and anything else you think belongs to the mind. But how can “I think” establish the existence of a subject that does these other things? How can we assert anything like “I think, therefore a subject of desire exists?” Thinking doesn’t entail desiring (imagining, etc.)! All that I can infer from “I think” is that a certain part of me exists—the part that thinks. But that is not all that I am qua conscious subject, so this multifaceted self is not demonstrable via the Cogito. In order to prove the existence of that self we will need separate arguments corresponding to each mental attribute: e.g., “I desire, therefore the desiring part of me exists”. But this doesn’t prove the existence of a unitary self—the self I take myself to be. It just proves the existence of many subjects of consciousness corresponding to each mental attribute I possess. But that is not what I am, i.e., a unitary being—unless we take the view that the self is actually not unitary but merely an assemblage of separate parts. The trouble with that view is that it is false: that is not what I am. So, the reconstructed Cogito does not deliver the self that actually exists, but only some watered-down conglomerate. Strictly, it only delivers a small part of the self as normally conceived—the part that thinks. The Cogito should read “I think, therefore a thinking thing exists”—with no implications for the existence of a self that thinks and desires and imagines, etc. But that is obviously not what the self is as we normally understand it, a thing that merely thinks. This is a thin surrogate for that familiar self. In fact, I know quite well that I am a unitary self with a variety of mental attributes; it is just that this knowledge is not vouchsafed by the Cogito. Indeed, the correct conception of the self is along the lines of “a single unitary embodied conscious subject enduring over time”: but the existence of that self is certainly not demonstrated by the Cogito. So, the Cogito does not establish the existence of the self—as it really actually is. At best it gives only an aspect or part of the actual real self. If I know that that self exists–and surely, I do know this–it is not by means of the Cogito; it might well be by means of ordinary observation, internal and external. Descartes wanted a skepticism-proof demonstration of the existence of the self, but he devised no such thing; the lesson should be that there is no skepticism-proof demonstration of the existence of the self, not as it normally (and correctly) understood. However, the Cogito can be used to prove the existence of other things, arguably important and surprising things; and thus, it provides a way out of solipsism and the mere existence of thoughts. Some of these are obvious, but some are not. First, it proves that there are mental attributes, since thinking is a mental attribute. I am certain that I am thinking (“there is thinking”), and I am certain that thinking is a mental attribute, so I am certain there are mental attributes. I am also certain that thinking is not a physical attribute, given that thoughts are not extended and extension is the essence of the physical. I also know with certainty that I know these things, since I can see that they follow logically from “I think”. Furthermore, I know that at least one token thought exists, and not just the type thought; so, I know that my thinking exists in time (token events need time to occur in, unlike types). In addition, I know that concepts exist, since thoughts are made up of them: there is no such thing concept-free thought. I also know that propositions exist, since thinking is a propositional attitude; so, I know that concepts combine into propositions. All this is obvious and easily deducible, but it doesn’t stop there. Don’t I also know with certainty that my acts of thinking are caused, given that all events have a cause? And if I know that, don’t I also know that my thoughts are governed by laws, given that causation implies laws? Thus, I can put together what I know by introspection with what I know a priori and derive some moderately interesting results. Some of these results have existential implications such as the existence of events and laws: thinking consists of token events with causes and causes require the existence of laws to back them. And now we might see our way clear to more surprising deductions: for example, that my thoughts must have a physical substrate. For, if events of thinking are subject to causal laws, but there are no causal laws of thinking per se, then these events must fall under other laws, and these would have to be physical (Davidson’s argument). If we combine this argument with the “I think” of the Cogito, we reach the conclusion that I have a brain! My point here is not to endorse that argument but merely to illustrate that there is room to get beyond the mental world that is demonstrated by the Cogito. We might also construct an argument establishing that space must exist if thoughts do, because time requires space, or because it makes no sense to postulate a world of individuated concrete events outside of space. We can thus work out from the Cogito to more adventurous conclusions aided by suitable a priori principles.[1] The certain knowledge that I think can be made to yield results independent of the traditional Cogito, which is dubious for the reasons given above. This procedure may not be skepticism-proof but it may be sufficient to generate knowledge of matters that transcend the mere awareness of thinking. The general idea behind the Cogito was essentially sound, although the traditional move to the existence of the self doesn’t work. If so, both Descartes and Lichtenberg were wrong: we can’t get the self from “I think” but neither is it true that we can get nothing but the existence of thoughts.

[1] I am not saying that this is easily done, or even that it is ultimately possible; I am merely saying that it is part of the intellectual landscape and not to be dismissed out of hand. It is a project worth pursuing.