Causality

When Hume watched billiard balls collide, he realized something unsettling: we never actually see causation itself, only one event followed by another. All our scientific confidence rests on custom and habit—we've seen balls collide thousands of times, so we expect it to happen again. This doesn't prove the future will resemble the past; we simply can't help believing it will. Hume essentially asked: what if causality is just a story our minds tell to make sense of otherwise disconnected events?

Kant reportedly said that Hume "interrupted his dogmatic slumber," prompting him to rebuild causality from scratch. Rather than finding causation in the world, Kant argued it's a built-in feature of how our minds organize experience—we can't perceive anything without automatically structuring it through cause and effect. It's like wearing glasses you can never remove: causality isn't discovered "out there," it's the lens through which we must see everything. This radical move transformed causality from a questionable observation about nature into a necessary condition for having any experience at all.

Neuroscience has discovered that your brain sometimes creates the sensation of causation backwards. In Benjamin Libet's experiments, people's brains showed decision-making activity up to half a second before they consciously "decided" to act, yet subjects felt they had consciously caused their actions. Your experience of willing something to happen may actually be your brain's post-hoc rationalization of what it already set in motion. This suggests our intuitive sense of personal causation—the feeling that "I" cause my actions—might be as constructed as Hume suspected.

Einstein's famous objection that "God does not play dice" was really about causality—he couldn't accept that quantum events might occur without causes. Yet decades of experiments suggest some quantum phenomena may be genuinely random, not just unpredictable due to ignorance. This isn't merely academic: technologies from transistors to quantum computers depend on this acausal behavior, and some physicists argue the universe itself might have emerged without a cause. The deepest level of physical reality may vindicate Hume's skepticism in ways he never imagined.

Ice cream sales and murder rates are strongly correlated, but eating ice cream doesn't make you homicidal—both increase in summer heat. This classic example reveals why distinguishing causation from correlation matters desperately in medicine, policy, and everyday decisions. When you read that "coffee drinkers live longer," are you seeing causation or just the correlation that health-conscious people drink moderate coffee? Hume's problem isn't just philosophical—it's why randomized controlled trials exist and why your intuitions about cause and effect can lead you seriously astray.

Some interpretations of physics permit retrocausality—effects preceding their causes—creating genuine paradoxes like killing your grandfather before he meets your grandmother. Philosopher David Lewis argued such scenarios are logically possible but practically constrained: you could travel back in time, but whatever you do must be consistent with what already happened. This isn't just science fiction: quantum experiments like the delayed-choice experiment suggest future measurements might influence past states. The universe might be far stranger than Hume imagined, where the arrow of causation doesn't always point forward.