Knowledge of One’s Own Existence
Alice dropped the fan “just in time to avoid shrinking away altogether. ‘That was a narrow escape!’ said Alice, a good deal frightened at the sudden change, but very glad to find herself still in existence”(Alice in Wonderland, p. 23). There is something conceptually peculiar in the idea of finding oneself to exist (as Lewis Carroll was surely aware), as if this could be any kind of discovery; the knowledge that one exists is not knowledge one acquires or picks up or happens upon at some particular time. It makes perfect sense to speak of being glad to find out that someone else is still in existence, but not of finding out that you yourself are still in existence. For how could you not know that you exist?
This raises the question of how I know that I exist, if not in the discovery way. Let us assume both that I exist and that I know with certainty that I exist; the question then is by what means or method I have come to have this knowledge—how do I come to know my own existence? We can begin by asking how I come to know that other things exist. The short answer is that I notice them. Things appear to me perceptually, and I form the belief that these things exist (rightly or wrongly). It looks to me as if there is a tree in front of me, and I form the belief that there is. The same is true of other people: people appear to me, and behave in certain ways, so I form the belief that they exist. I notice things in the world, as it appears to me, and I form existential beliefs with regard to these things. But is that the way I form the belief that I exist? Do I perceptually appear to myself? Of course, I can and do perceive my own body; but that is not how I come to know that I exist, for familiar reasons (I could know that I exist without ever observing my body, or even without having a body). It is not that I notice myself among other appearing objects and then venture the opinion that I exist. Nor does anyone inform me that I exist (though they may inform me that Colin McGinn exists). I have non-observational knowledge of my existence; and I can’t be wrong. Even if I did appear to myself, or observe myself, or notice myself, that could not be the basis of my knowledge that I exist: for I can only be appeared to if I exist. Just by being a subject of appearances I exist, so it can’t be that I ground my knowledge that I exist on the fact that I appear to myself: even if I didn’t appear to myself, I would know that I exist, just by the fact that I am appeared to at all—by any kind of entity. I am unique among empirical particulars in that I know myself to exist independently of appearing to myself.
But how then do I know that I exist? Here is where things become difficult, because nothing obvious suggests itself. The Cartesian line is that I infer my existence from the fact that I think (“I think, therefore I am”), but surely my knowing that I think presupposes that I exist—it is not the ground of that existential belief. I don’t form the belief that I exist by noticing that I think and then making an inference to a new piece of knowledge. I know that I exist before making any such inference. It does not seem that I infer my existence from anything—I just know it. Did Descartes really not know that he existed until he formulated the Cogito? Is that how children come to know they exist? Is there even a specific time at which people come to know that they exist (this is not the same as the question of when they first say they exist)? Other existential knowledge has its time and place of origin, but was there ever a moment at which you realized that you exist? Was it when you first noticed yourself thinking? Were you in the dark as to your existence beforehand, full of doubts? We don’t, to paraphrase Alice, find ourselves one fine day pleasantly surprised to discover that we exist, like a diamond buried in the garden: our existence does not occur to us or dawn on us or come to us as a revelation. By contrast, my knowledge of the existence of other people, though long possessed, did have a time of origin. But I never found myself wondering if I exist and then coming upon evidence one day that I do. I don’t need any evidence to know that I exist. I just know it.
We might conclude from this that knowledge of one’s own existence is not a posteriori—we don’t know it “by experience”. That seems right: we know the existence of other things and people by experience but not the existence of ourselves. Is it then a priori? Well, it is not much like mathematical knowledge, and it doesn’t arise from some sort of rational deduction. It is evidently sui generis–neither a posteriori nor a priori. It belongs in a class of its own. Not all knowledge falls neatly into one of those two broad traditional categories. We don’t know it by means of the senses (including introspection), and we don’t know it by means of rational intuition. We know it, apparently, by no means at all—except by being the thing that is known. It is like one’s knowledge that one is a person: I don’t know that I am a person by sensing or inferring that I am a person, but neither do I know it by rational intuition—I know it by being a person. Once I am able to think of myself as a person, I know that I am a person, because that is what I am—a thing that knows that it is a person by being a person. Similarly, to be a conscious reflective being is to know that one exists; no further conditions need to be met, such as having evidence for one’s existence. I know that I exist, not by being presented to myself as myself, but by being something that must exist in order to be presented by anything: in being presented by a tree I must exist in order to be so presented—whether the tree itself exists or not. I don’t know that I exist by being, or becoming, acquainted with myself, as Russell would say, but by being acquainted with things other than myself—while recognizing that a precondition of this is my own existence. I therefore know that I exist in a way that I know nothing else to exist. Knowledge of my own existence is a unique kind of knowledge: it doesn’t involve detecting anything.