Overgeneralisation vs Under‑generalisation: Ramsey’s Guide to Predicting the Future

How we navigate the future using generalisations

Generalising is not always a bad thing. While overgeneralising—drawing broad conclusions from limited evidence—can lead to harmful stereotypes, the process of generalising itself is a natural and necessary part of human cognition. Without it, we would struggle to make sense of the world. The challenge lies in knowing when and how to apply these generalisations effectively, as explored by philosopher Frank Plumpton Ramsey in early 20th-century Cambridge.

In 1930, philosopher Richard Braithwaite discovered handwritten notes by Ramsey, a brilliant thinker who died at just 26 but left a lasting impact on philosophy, mathematics, economics, and logic. In those notes, titled *General Propositions and Causality*, Ramsey challenged conventional views on generalisations, arguing that believing a statement like "all humans are mortal" is not about listing every individual case but about adopting a disposition—a habit of acting as if the generalisation holds true. This disposition shapes how we anticipate and respond to future events.

Ramsey’s idea emerged from his disagreement with the philosopher Ludwig Wittgenstein, whom he had worked with in Cambridge. Wittgenstein had argued that believing a generalisation like "all humans are mortal" meant accepting an infinite list of specific truths about every human. Ramsey rejected this, pointing out that two people could agree on all known facts about individuals yet still disagree about the generalisation. For example, a techno-utopian might accept that every human so far has been mortal but still believe immortality is possible. Ramsey’s view emphasised that generalisations serve a practical purpose: helping us navigate an overwhelmingly complex world by making predictions and simplifying decisions.

Not all generalisations are equally useful. Universal claims, such as "all cats are furry," can be easily disproven by exceptions like hairless Sphynx cats. Ramsey recognised that overly precise generalisations become cumbersome, burdened with too many exceptions. Instead, many of our everyday generalisations—like "cats are furry"—work well enough in practice, even if they aren’t strictly true in every case.

The lesson from Ramsey’s work is that generalising is not inherently flawed; it is a cognitive tool that helps us function. The key is recognising its limits and adjusting our habits accordingly.

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