The historians Thomas R. Cole and David Hackett Fischer have documented how, at the start of the 19th century, the idea of aging as part of the human condition, with its inevitable limits, increasingly gave way to a conception of old age as a biomedical problem to which there might be a scientific solution. What was lost was a sense of the life span, with each stage having value and meaning.

Perhaps this is why, as a 2006 study found, we mispredict the happiness we expect to feel across the course of our lives and assume that we’ll get more unhappy as we age. In fact, the research shows that the opposite is true. For my part, at 64, I haven’t attained serenity (another stereotype of older people), but I am more able to savor life — and if offered the chance to return to my 14-year-old self, I’d run screaming the other way.

A student of mine, nudging 60, recently called age “the great liberator.” Part of what she meant was that old people simply care less about what others think, but also, I think, that our sense of what’s important grows with age. We experience life more intensely than before, whatever our physical limitations, because we know it won’t last forever.

How to enable the growing numbers of old people to live comfortable, meaningful lives is a fundamental issue of equality, with benefits for all. If we make the world better for old people, we make it better for everyone, from stroller-pushers to wheelchair-users.