One’s Own Mind
Several times in The Basis of Morality Schopenhauer remarks on the mysterious nature of compassion (or altruism). He says: “When once compassion is stirred within me, by another’s pain, then his weal and woe go straight to my heart, exactly in the same way, if not always to the same degree, as otherwise I feel only my own. Consequently the difference between myself and him is not an absolute one.” (85) This is followed by: “No doubt this operation is astonishing, indeed hardly comprehensible. It is, in fact, the great mystery of Ethics, its original phenomenon, and the boundary stone, past which only transcendental speculation may dare to take a step.” (88) In the Appendix Schopenhauer returns to the mystery and proposes to explain it (though not without introducing further layers of mystery). His basic idea is that there is in fact no deep distinction between what we regard as separate selves: we are all one at the level of Kantian noumena—the “intelligible self” (as opposed to the “phenomenal self”) is a single entity. This means that all so-called compassion (altruism) is a species of egoism, since to benefit others is to benefit the noumenal self that I ultimately am. I am you, so concern for you is concern for myself. He writes: “Now, as regards that side of the self which falls within our ken, we are, undoubtedly, sharply distinguished, each from the other; but it does not follow therefrom that the same is true of the remainder, which, surrounded in impenetrable obscurity, is yet, in fact, the very substance of which we consist. There remains at least the possibility that the latter is in all men uniform and identical.” (136) He goes on to argue that space and time individuate phenomenal selves, but noumenal selves do not exist in space and time, and so are free to coincide according to their transcendent nature. The plurality of selves is an illusory product of the human spatiotemporal form of subjectivity; beneath it a monism of the self reigns. As Schopenhauer remarks, this doctrine of Self-Monism is of ancient origin and distinguished lineage (though more in the East than the West): he mentions the Upanishads, Pythagoras, Spinoza, the New Platonists, and others. Hoping to make the view more palatable and down-to-earth, he compares it to dreams: “For just as in dreams, all the persons that appear to us are but the masked image of ourselves; so in the dream of our waking life, it is our own being which looks on us from out our neighbors’ eyes,–though this is not equally easy to discern.” (141) So-called other minds (selves) are my mind (self) elsewhere.
This is no doubt a startling, not to say vertiginous, doctrine, hardly calculated to elicit immediate assent; indeed it may appear quite batty. But perhaps it can be given a more quotidian rationale—perhaps we can even argue in its favor. It may turn out to have roots in familiar observations about the nature of the self. At any rate, I propose to inquire whether the doctrine admits of something like demonstration, or at least to break down intuitive resistance to it. Can it be ruled out a priori? Does it describe a logical possibility? Is it upon closer examination a rather natural view to adopt when once we take the true measure of the self as ordinarily conceived? Let us begin with a datum: when one person encounters another the fact of bodily separateness is a presentation of perception (an “impression”), but the fact of personal separateness is not. Your body looks to be separate from mine, at some distance from mine, but your mind doesn’t look to be separate from mine, at some distance from mine. I see your body in space located at a certain position, which is not where I see my own body as located: but I don’t see your mind as similarly located in relation to me. If it is separate from my mind, this separation is not a perceptible fact—not a fact of “intuition”, as Kant would say. Rather, it is matter of inference, of belief, of hypothesis even. It is not a given. So why do we think this way—is it a justified assumption? How can we rule out the idea that what you assume to be another mind is just your own mind in another guise? To answer this question we need to venture out into modal space. Is there a possible world in which a single mind is distributed across a plurality of bodies? That does not seem difficult to conceive: the several bodies, with their accompanying brains, work together to realize a single mind, functionally and phenomenologically unified. There might be coordinating communicative contact between these bodies that keeps them on a single track. Social groups can be functionally unified; well, in this possible world the bodily group houses a single mind. Our brain, after all, consists of a grouping of separable organs occupying different positions—why not conceive of a mind that takes this arrangement a step further? Thus when these bodies encounter each other they are encountering a single mind multiply located. People sometimes speak of a “hive mind” to describe highly social species like bees and ants: couldn’t there be a world in which this is literally true of some organisms–one mind existing in many bodies? Or suppose a scientist was to remove one of your cerebral hemispheres as you slept and insert it into another body: couldn’t you find yourself (unbeknownst to you) talking to someone that literally has your mind in his body? That is, there is now a mind that is partly in one body and partly in another. And couldn’t this process in principle be repeated to produce many bodies sharing a single mind? How do we know this wasn’t done to all of us by super-extraterrestrials years ago? It isn’t logically or conceptually excluded. What if some tech billionaire had his mind uploaded into many different bodies: wouldn’t this be a case of a single mind in many bodies? Couldn’t your unconscious mind be located in a different body from that housing your conscious mind? You might then be able to chat with someone whose brain holds your unconscious mind (yours is already full of your conscious mind). The possibilities are endless. So Self-Monism is metaphysically possible: there could be a possible world in which a single mind shares many bodies. It doesn’t of course follow that our minds could exist in such a form, but it does show that some mind could—the idea is not contradictory or metaphysically impossible.
What makes minds (selves) distinct? If minds are individual brains, then it is the spatial separation of brains: this kind of materialism thus implies that human minds are a plurality, because brains are. But if dualism is true, then we don’t have spatial separation to deliver the individuation conditions of minds: what then makes suchminds separate? What indeed? In fact, it is hard to see how dualism doesn’t lead to self-monism: for how can disembodied minds maintain their non-identity? Here matters become obscure: what is the principle of individuation for minds under dualism? Causal connections to the body won’t do it, since there is nothing to prevent different immaterial minds from interacting with the same body, or the same immaterial mind interacting with many bodies. In the case of dualism, space can’t ensure plurality, so dualism looks like it will entail the identity of all minds; in any case, something would need to be said to prevent this result. What seems clear is that nothing we know rules out the identity of all human selves: it is an epistemic possibility that this is so. The mind of a fellow creature might be a part of my mind, as my mind is a part of its (human or animal). The relation between my mind and other minds might be like the relation between different regions of the same country: both are parts of a larger whole. When I speak of “my mind” I actually refer to this larger entity—as it might be, the Kant-Schopenhauer noumenal single self, or a vast Humean totality of atomic “ideas”. To be sure, I am not aware of all my mental states, as I am not aware of the states of my unconscious; they are distributed across many sub-minds that together compose the single overarching mind. We can model this set-up on what we know of the individual mind: it too is composed of a number of sub-minds (“modules”) that don’t always have access to each other. The individual mind is really a composite structure—a kind of hive mind. Thus we entertain such notions as multiple personality, hemispheric specialization, separate computational modules, cooperating homunculi, and so on. If the mind of man is already a congeries, why can’t what we think of as an individual mind be made up of smaller minds distributed across organisms? Why make such a sharp distinction between one mind and another if one’s own mind is a mixed bag of sub-minds? Why not believe in the extended mind in the sense of one mind existing across separate bodies? Why let the way bodies look shape the way minds are individuated? Doesn’t this give rise to an illusion of separateness on the part of minds? If we lived in a world in which self-monism is stipulated to be true, it would still look to us as if self-pluralism were true, simply because of the nature of perception of the physical world—we would jump to the conclusion that selves had to be distinct. We tend to think the mind is more unified than it is, based on introspection and perception; and we also tend to think it is more isolated than it is (according to self-monism), based on the way we perceive the world.
This is not to prove the truth of self-monism but rather to break down barriers that rule it out a priori. For it is certainly true that we don’t perceive the truth of self-monism: minds don’t look as if they are all part of a larger mind. That is a metaphysical speculation, prompted in the first instance by the mystery of compassion. It explainswhy compassion is based on sound metaphysical instincts: it is not just as if I am present in the other feeling his pain but I actually am there. He is part of me. In order to prove this we would have to show that the idea of many separate minds is impossible—that minds must form a unity. Such a proof might take the form of showing that nothing could give rise to a distinction of selves, because space can’t do it and nothing else is available to play the individuating role of space. I haven’t given any such proof (and neither has anyone else that I know of), but I have given reason to think that the view in question is not devoid of coherence and motivation. Schopenhauer thinks self-pluralism is a prejudice of the West, arising perhaps from the Christian religion (individual salvation) or the politics of capitalism or too much empiricism; we might be able to shed it by enlarging our imaginative possibilities. Maybe if we tried thinking of other people and animals as parts of ourselves, in order to strengthen the grip of altruism, we would come to find the view natural as well as ameliorative. It might become second nature to us. My mind doesn’t leave off where my body ends but extends into the minds of others in a wonderful mystical synthesis! My mind and your mind are joined at the hip, so to speak. Perhaps the question ought to be: How do I know that your mind isn’t mine?
 If altruism appears less altruistic under self-monism, egoism is less egoistic under a more pluralistic view of the individual self: if each self is a congeries of mental elements, then there is a question as to which of them a given act benefits. Thus we can distinguish between benefiting my higher self or my lower self, my id or my superego. Egoism will be relative to a chosen sub-self, some closer than others to what I regard as my central self. I could be quite cruel towards one of my sub-selves (think of split-brain patients).
 There is a similar question about the individuation of things like angels or gods: how can we make sense of qualitatively identical but numerically distinct examples (tokens) of these types, given that spatial separation can’t do the job? Compare: how do Cartesian minds differ numerically if they are qualitatively identical?
 It might also be suggested that our language encourages the illusion of self-plurality in addition to the way we see things: the personal pronouns make it seem as if persons are rigidly distinct from each other. I am not you, sheis not him, and this person is not that person. The words are clearly distinct, but are the denotations?