The Problem of Causality

David Hume was born on May 7, 1711, in Edinburgh, Scotland. His central insight was simple and unsettling: we cannot prove that the future will resemble the past. Just because the sun has risen every day does not logically guarantee it will rise tomorrow. Causality, the bedrock of science and everyday reasoning, is not something we can deduce. It is something we assume, based on habit.

When we see a billiard ball strike another and the second moves, we conclude causation. But Hume pointed out we never actually observe causation -- only sequence and correlation. The rest is inference built on repeated experience, not logical necessity. This was a problem for science, which relied on the assumption that natural laws are consistent. If Hume was right, induction itself had no rational foundation. He did not propose a solution. He simply pointed out that reason alone could not solve the problem.

His skepticism extended beyond causality. He questioned the self as a continuous, unified entity. When he looked inward, he found only a stream of perceptions, but no enduring self beneath them. Identity was not a thing. It was a pattern recognition problem.

portrait of david hume by allan ramsay, c. 1754, national galleries of scotland. source: wikimedia commons

Immanuel Kant said Hume woke him from his dogmatic slumber. Karl Popper built a philosophy of science around the idea that theories can only be falsified, never proven. Machine learning systems today are fundamentally Humean: they identify patterns and generalize, with no deeper understanding of why those patterns exist. Hume died in 1776, untroubled by the implications of his own philosophy.

What Hume left behind was not a system but a challenge. Every designed system, every algorithm, every prediction rests on the same assumption: the patterns we have seen will continue. Hume would say that is faith, not reason. And he would be right.