One simple explanation is that mutual circumstances and emotions are often the links that draw people together, creating bonds and relationships that ward off loneliness and solitary existence. A stranger becomes a friend when you know someone in common, or work at the same place, or follow the same bus route. In these cases, you both understand something about how the other person feels in a shared circumstance, which provides a context that connects you to one another. For example, because you can imagine that it is painful to lose someone close to you to a sudden illness, even if you have been fortunate to have never experienced such a situation, you can understand that a small gesture of kindness, whether a small note or a batch of home-baked cookies, will be welcome. The care we demonstrate to others, the anxiety about their well-being, and the genuine desire to see a smile blossom across a loved one’s face all stem from knowing that if you were in his or her body, you would feel the same pain, loss, or sadness. At the same time, when your friend lands a new job or you arrive at your twenty-first birthday, you wish to share the excitement and joy. We perceive how good news makes us feel, and realize that others can be genuinely happy when we are happy, just as our own happiness derives from theirs.
Empathy is equally important when we have become habituated to the same, seemingly endless routine, when everything that is different is merely peripheral and each day is like yesterday on repeat. We become slightly desensitized to the world around us, slowly forgetting the textures of life, the same way you might become accustomed to the feeling of prickly wool on your skin after a few hours of wearing a knit sweater. Empathy can introduce a heady wave of emotion, reminding us that there is more to Thursday than the blur of the commute and the hands of a desk clock ticking by. Six o’clock P.M. might mean a crammed bus back home for me, but it might mean the incoming of high tide to a hermit crab, or the beginning of the forage for a moth-eating bat, or the arrival of curfew to the residents of a far-away city where the rules and customs are quite different. Where would I go and what would I do at six o’clock P.M., if I weren’t me?