Two pool balls

About this video

Tom is playing pool. He hits the white ball, it rolls across the table, touches the red ball, and the red ball rolls into a pocket. Everyone would say the white ball made the red ball move. But look closely at what you actually see. Can you see the making?

The Scottish philosopher David Hume asked this in 1748, with the same example of two balls. When we look, he said, we see the white ball move, then the balls touch, then the red ball move. That is all. We don't see a third thing - the push, the "making" - passing from one ball to the other. So how do we know the white ball made the red one move? Because we have seen things like it many times. Someone who had never seen anything move, shown the white ball rolling for the very first time, could not tell what would happen next: the red ball might stay still, or fly upwards. Only by seeing the same thing follow again and again do we learn what causes what.

There are two answers about what a cause is. Hume's own: a cause is what is always followed by its effect, and the feeling that the first must bring the second is our habit of expecting it. The puzzle for this answer: night is always followed by day, yet night doesn't cause the day; both come from the Earth turning. The other answer: things really have powers to make things happen. Sugar has the power to dissolve in water, a glass is breakable before it breaks. The puzzle for this answer: what is a power, if nobody can ever see one? It seems we believe in powers only because of what we see follow, which brings us back to Hume. The question is still argued about. This video goes with the Can You See a Cause? lesson of Metaphysics Level 1 on Knaph.

Transcript

1. 0:00The white ball hits the red. The red rolls into a pocket.
2. 0:05Hume asked what you see. One movement, then another. Never the making.
3. 0:11The first time, you couldn't tell what comes next. We learn from repeats.
4. 0:17Hume. A cause is what always follows, plus habit. Yet night doesn't cause day.
5. 0:23Or things have real powers, like sugar's power to dissolve. But who has seen one?
6. 0:29Habit, or a real power?