AFTER John Locke published his Essay Concerning Human Understanding in 1690, he sent copies to various savants of his acquaintance, asking for comments and in particular for advice on whether he had left out anything essential – for if so, he could add it to a second edition. His correspondent William Molyneaux of Dublin replied that Locke needed to say something about personal identity: that is, what makes a person the same person throughout their life.
Belief in the idea of a substantial soul – a “you” that is separate from your body – was waning. In the absence of this…
