You've never actually seen a cause

Watch one billiard ball strike another and roll it forward. You'd swear you just witnessed cause and effect. But the 18th-century philosopher David Hume pointed out something unsettling: you didn't. You saw one ball move, then contact, then a second ball move. What you never saw — never could see — was the invisible necessary connection that supposedly forces the second event to follow the first.

All we ever actually observe, Hume argued, is constant conjunction: event B reliably following event A, over and over. The extra idea that A makes B happen isn't in the sensory data at all. Instead, our mind forms a habit — after enough repetitions, we automatically expect B when we see A, and we project that feeling of expectation onto the world, calling it 'causation.'

This is Hume's famous challenge to induction: no amount of past regularity logically guarantees the future will behave the same way. The sun rising every day doesn't prove it rises tomorrow; we just can't help believing it will. Causation, on this view, is less a fact we discover out there and more a story our minds are wired to tell.