David Hume, the great eighteenth-century Scottish philosopher, found the origin of ethics to be firmly in our feelings, and based his ethics on an empirical analysis of our nature as a species. Hume’s simple analysis of compassion and sympathy is one of the high points of European ethics and anticipates contemporary scientific thinking about empathy. Hume imagined no great original catastrophe in human morality, but regarded our emotions and our imagination as the source of our ethics. Hume understood emotions as our inner agitations comparable to our immediate bodily senses like sight, taste, hearing and touch. If our "impressions of sensation” are stimulated by light, heat, flavour and sound, then our sympathy is shaped "by some particular turn of thought and imagination” that reflects upon our feelings. For Hume, the power and universality of our feelings and our ability to imagine what others are feeling are what makes us moral and concerned for others.
In his famous analysis of compassion in his 1739 Treatise on Human Nature, Hume describes sympathy as the universal emotion through which we identify ourselves with others in distress. Sympathy emerges because of our innate resemblance to others and is felt instantaneously as our imagination thinks about their situation:
We have a lively idea of everything related to us. All human creatures are related to us by resemblance. Their persons, therefore, their passions, their interests, their pains and pleasures must strike upon us in a lively manner, and produce an emotion similar to the original one [that the other person experienced]... If this be true in general, it must be more so of affliction and sorrow.7
For Hume, this combination of shared feelings and imagination creates “the general rule of sympathy” across human society. He describes an almost neurological process in which thinking makes an “impression” on our passions, which then create an emotion proportionate to the idea we have had. It is by thinking and imagining that we feel with and for another person. To show how quick and visceral is the process of sympathy, Hume uses the example of a woman who faints at the mere sight of an unsheathed sword, even though it is in the hand of her friend, because she thinks about (and so feels) the pain and damage it could inflict.8
This insight into the immediate and visceral effect of the suffering of others upon our emotions is, of course, not new. The imitative power of drama and its ability to affect us instantly and deeply was well observed by Aristotle, writing in the fourth century BC. In his Poetics, discussing the best kind of tragedy in Greek theatre, Aristotle recognizes our ability to feel instinctively for others: “the plot should be constructed in such a way that, even without seeing it, anyone who hears the events which occur shudders and feels pity at what happens: this is how someone would react on hearing the plot of the Oedipus.”9
Like Aristotle, Hume believed our feelings are contagious. The actual sight and sound of another’s suffering, or the imagination of people’s pain and predicament, are physically shared around. Like notes along the strings of a musical instrument, we humans can vibrate as one: “As in strings equally wound up, the motion of one communicates itself to the rest; so all the affections readily pass from one person to another, and beget correspondent movements in every human creature.”10
Hume’s friend and Scottish compatriot, Adam Smith, also placed sympathy at the centre of his great work on ethics, The Theory of Moral Sentiments. Writing twenty years after Hume’s Treatise, Smith started with the famous lines:
How selfish soever man may be supposed, there are evidently some principles of his nature, which interest him in the fortune of others, and render their happiness necessary to him, though he derives nothing from it except the pleasure of seeing it.11
Smith too called this phenomenon sympathy or "fellow feeling” and also saw imagination as its source: our ability to conceive of others’ suffering and feel it as our own, albeit inevitably to a lesser degree than the person suffering.
In their attention to sentiment, Hume and Smith were following the great Italian medieval Christian theologian Thomas Aquinas, who had recognized compassion or misericordia as the instant heartfelt emotion in which we feel the suffering of others as if it were our own and which then prompts us with a desire to act in order to relieve their suffering.12
Hume and Smith were both convinced that the rule of sympathy or fellow feeling extends universally across the world but is inevitably reduced in power, but not in principle, by distance between people. Our actual ability to feel for people far away is not the same as our ability to feel for people who are near us or whom we know. The range of our sympathy varies but not the moral principle of care and concern that creates it. So passion varies, but principles do not:
We sympathize more with persons contiguous to us, than with persons remote from us: more with our acquaintance, than with foreigners. But not withstanding this variation of our sympathy, we give the same approbation to the same moral qualities in China as in England.13
What is cruel and painful remains so, whether you know about it or not; but distance makes a difference to how we feel. Scale matters too. Modern psychological studies show clearly that there are quantitative limits to affect, and that larger numbers tend to move us less. Paul Slovic at the University of Oregon has coined the term "psychic numbing” to describe what happens to us when we are faced with the enormous numbers of dead and suffering in mass atrocities. He and his co-authors show how very large numbers far away "do not feel real”, and suggest that our moral intuition seems to fail when faced with truly massive suffering. We cannot truly envisage it and our ethical response short-circuits to a certain kind of numbness. We care but cannot really imagine enough to trigger a proportionate sense of outrage and action. This numbing presents hard problems for mobilizing humanitarian and political action around mass atrocities. It is also the reason why "when it comes to eliciting compassion, the identified individual has no peer” in marketing and mobilizing humanitarian concern.14 Our sympathy, although essentially universal, does have limits, it seems. If we cannot really imagine suffering, we cannot really feel it and so we fail or struggle to respond to it. Hume and Slovic are both realistic about the limits of compassion in global politics.