No idea is so antiquated that it was not once modern. No idea is so modern that it will not someday be antiquated.

Glasgow’s aphorism compresses a historical view of ideas into a neat symmetry: what we dismiss as “outdated” was once the cutting edge, and what we celebrate as “new” is already on its way to becoming old. The point is less cynical than clarifying. It warns against intellectual snobbery (mocking the past as merely benighted) and against presentism (treating current fashions as final truth). Implicitly, it invites humility and historical imagination: ideas live in cycles of adoption, institutionalization, and replacement, shaped by changing needs and contexts. The quote also suggests that “modernity” is a moving label rather than an intrinsic quality of an idea.