Brain imaging and the inner life

Abstract

“The intense intellectual and emotional life, and the heightening of sensations which came with the advance of civilization, made it clear to men that only a part of pain, pleasure, and profit of life lay in physical things. Thoughts, emotions, and sensations demanded legal recognition”, wrote Samuel Warren and Louis Brandeis in the landmark 1890 paper that first introduced the right to privacy to legal discourse. Warren and Brandeis saw themselves as articulating a moral idea that was already implicitly recognised but finally forced into the open by “recent inventions and business methods”—that is, by “instantaneous” photography and tabloid gossip columns. Warren and Brandeis were giving legal voice to the increasing demand for privacy that accompanied the rise of the middle classes in western countries during the 19th century. The Victorians were greatly preoccupied with the inner life. Indeed, William James's The Principles of Psychology, with its vivid metaphor of the stream of consciousness, was also published in 1890, and by then his brother Henry James and other novelists had already embarked on the great modernist project of capturing in prose that hidden stream of thoughts and sensations—letting their readers peer into another's inner life, seen as if through a transparent glass. Having just been “discovered”, privacy's limits were soon put to the test in the 20th century. The threat was not gossip columns, but the totalitarian state, where one's closest and dearest might be secret informants and even trivial acts might be dutifully recorded in the state's black books. But even when George Orwell famously tried to imagine a dystopian world with no privacy, state supervision went no further than the boundaries of the mind itself. Orwell's 1984 portrayed a genuine, horrifying possibility, but for all the talk about Big Brother and brainwashing, the idea of literally invading another's consciousness still seemed no more than fantasy. After all, although the idea of a right to privacy may be recent, the impenetrability to others of the inner life is as old as the mind, part of the unthinking background to human life. The privacy of the inner life may be as old as the mind—but perhaps its days are numbered. Recent advances in brain imaging technology perhaps begin to raise the possibility that at some future point there will exist “brain reading” technology that could reveal what is silently contemplated in the recesses of the mind, requiring us to literally give legal status to thoughts, emotions, and sensations. To be sure, brain imaging is still in its infancy. But neuroscience has already begun to map the neural correlates of our inner life. Research is underway to identify the neural signature of lying, to tell which of several intentions is chosen, and to identify the objective correlates of the subjective experience of pain. We do not yet know the empirical limits of neuroimaging, but philosophers already can and should raise general questions about the conceptual and ethical limits of neuroimaging. One set of questions comes from the philosophy of mind. Is it even coherent to talk about “brain reading”—about peering into another's stream of consciousness by scanning their brain? What conception of the mind does this presuppose, and is this conception philosophically sound? We need to resist the temptation of a misleading Cartesian conception of the mind as at once completely transparent to self and utterly impenetrable to others. This conception overlooks the intimate conceptual tie between the inner and the outer: our concept of the mental is such that it is of the very essence of thoughts and feelings that they can be expressed in public words and deeds. What we know about others on the basis of their behaviour is not merely “second best” knowledge, let alone mere conjecture—indeed, we often know others better than they know themselves. It is thus a mistake to think of the inner as a “Cartesian theatre”—to borrow Daniel Dennett's phrase in Consciousness Explained—to which others have no entry but that we ourselves can infallibly perceive from a distance of zero. As much recent philosophy of mind has taught us, a given mental state has a particular content—is about someone or something—only through its systematic interrelations with other mental states and with complex patterns of dispositions to behaviour. And philosophers of mind have further taught us that our minds' contents might be partly constituted by our relations to our external environment or a certain community. Indeed, this counter-Cartesian conception of the mind might make it seem confused to even think that we could ever know what is in a mind simply by peering into someone's brain. This is one way of interpreting Ludwig Wittgenstein's remark in Philosophical Investigations that “[i]f God had looked into our minds he would not have been able to see there whom we were speaking of”. If God couldn't see this by peering into consciousness itself (whatever that means), wouldn't it be complete confusion to think that we could do better by looking at patterns of brain activation? But this, I think, goes one step too far. The idea of “brain reading”, however difficult to realise empirically, is actually conceptually modest. It does not presuppose that thoughts and feelings are just neural processes with “contents” that can be read by simple inspection. The contents of our inner thoughts may, indeed, be no more transparent than words sincerely written down in a diary, but this hardly means that they would be more opaque. In interpreting the deliverances of “brain reading”, we will be able to know what another is thinking in the usual way that we can know what another is saying—by taking for granted a certain set of background beliefs and desires, by relying on context, and by assuming certain connections to the natural or social environment. Wittgenstein's remark is not, I think, best understood as a denial of God's omniscience. It is a denial that God could know the content of a thought just by peering into a mind. But that is not a problem, since God would presumably also know whatever else is relevant to determining its content. And although we will usually know less, we will almost always know enough. I doubt that conceptual arguments about the nature of mind can somehow magically rule out the possibility that neuroimaging will one day make the inner transparent to others. And this takes us to a second, ethical set of questions. When I consider a future in which our minds would be exposed to others, my first reaction is horror. If others were able to directly inspect my thoughts and feelings, wouldn't I be completely exposed and vulnerable, mentally naked? However, such reactions to possible technological changes are not yet moral arguments. In the past they have often been badly mistaken: windmills weren't instruments of Satan, as William Blake had feared in Jerusalem. Would invasion of our stream of consciousness really be of an entirely different moral order than more familiar threats to privacy? Moreover, is there a deep moral difference between wiretapping and “mindtapping”, between browsing someone's private diary and peeping into her brain? Not everyone thinks there need be a deep difference. Wittgenstein again serves as our foil when he remarks, in Philosophical Investigations, that “[o]nly God sees the most secret thoughts. But why should these be all that important? Some are important, not all. And need all human beings count them as important?” On reflection, it does seem that what matters for privacy is whether others know something personal about oneself, not how they came to know it. Psychologists have shown that many of our passing feelings are almost invariably expressed in facial micro-expressions that we do not notice, but which can, with training, be detected. Would it really morally matter whether I found out about your hopes and doubts by inspecting your brain or by tracking your micro-expressions? The difference between the two may only be a difference of degree, not of kind. Still, we should not underestimate its ethical significance: it might be a vast difference of degree. It is only a contingent fact that our inner lives are impenetrable to others, but this is a truly profound contingency, deeply embedded in our form of life, and although a world in which the mind is completely transparent is very distant, we should at least begin to reflect on what would be lost in such a world. Much might be gained: imagine a world with little, or even no, lying and deceit; a world in which there would never be an excuse for torture. This thought is not really a new one. In one of Aesop's fables, Momus criticises Jupiter because “he had not placed the heart of man on the outside, that everyone might read the thoughts of the evil disposed and take precautions against the intended mischief”. Immanuel Kant somewhere speculates that “on another planet there might be rational beings who could not think in any other way but aloud. These beings would not be able to have thoughts without voicing them at the same time, whether they be awake or asleep, whether in the company of others or alone.” Kant then asks “In what kind of different behaviour toward others would this result, and what kind of effect would it have in comparison with our human species?” As neuroscience advances, this might become a question about our own future.