Why the future doesn't have to resemble the past

HostIf you hold a pen out and let go, you know exactly what's going to happen. It hits the floor every single time. We spend our whole lives making bets like that, assuming the world will keep working the way it always has, but we rarely ask why we're so sure.

HostWhat's actually backing up that bet?

GuestIt's funny because the thing we rely on most is actually a bit of a disaster when you look at the logic of it. Philosophers call it induction. That's just a fancy way of saying we look at what happened in the past and assume the future will look just like it. Back in the seventeen hundreds, a thinker named David Hume pointed out that this is a huge leap of faith. He split things into two piles. One pile is stuff like two plus two equals four. That's true by the very meaning of the words. You don't need to go outside and check. But the other pile is what he called matters of fact, like the sun rising tomorrow. You can't prove the sun will rise just by thinking about it. There's no rule of logic that says it has to happen just because it happened yesterday.

HostBut it has happened every day for billions of years. Isn't that a proof in itself?

GuestThat's the trap. When you say it'll happen because it has always happened, you're using the past to prove the past. It's a circle. You're saying the future will be like the past because, in the past, the future was like the past. To prove that nature has steady rules that never change, you have to assume that nature has steady rules that never change. You're using the very thing you're trying to prove as your proof. Hume called this a scandal because it means the entire base of how we think about the world isn't built on a solid floor of logic. It's built on something much fuzzier.

HostSo if it's not logic, why do we all feel so certain about it? I mean, I would be terrified to walk out the door if I didn't think the ground would stay solid.

GuestWe do it because we have to. Hume said this belief isn't a choice we make with our big brains; it's a habit of mind. It's a custom. We're biologically wired to be habit-forming creatures. If an animal didn't learn that a certain smell meant food was near, or that a loud noise meant a predator was coming, it wouldn't last very long. It's a survival tool. We mistake a sequence that repeats for a link that must exist. We see A followed by B a thousand times, and our brains just weld them together. We don't have a logical right to be sure, but we have a biological need to be sure. Without that habit, you couldn't even trust that bread would nourish you or that the floor would hold your weight.

HostOkay, but even if we admit we're just guessing based on habit, isn't it still the best guess we have? We see green emeralds, so we assume emeralds are green. That seems pretty straightforward.

GuestIt feels that way until you realize that the same data can point to a million different futures. There was a thinker named Nelson Goodman who came up with a strange thought experiment to show this. Imagine a new word, grue. Something is grue if it's green right now, but it turns blue in the year twenty twenty six. If you look at an emerald today, it's green. That fits the theory that all emeralds are green. But it also fits the theory that all emeralds are grue, because we haven't reached twenty twenty six yet. Both ideas are backed up by the exact same evidence. We only pick green because it feels simpler or more natural to us, not because the emerald itself tells us which one is true. The data is silent about what happens next.

HostThat sounds like a bit of a word game. If I tell a builder to use green tiles and he uses ones that turn blue next year, he's just wrong. Logic has to weigh in at some point.

GuestThe point is that logic doesn't tell us which pattern to follow. We just pick the one that fits our past habits. But there's a way to handle this without pretending we have a crystal ball. Karl Popper suggested that science doesn't actually rely on proving the future at all. He said we should stop trying to verify our theories and start trying to break them. This is called falsification. In this view, we don't know for sure that the sun will rise tomorrow. We just have a theory that it'll, and that theory hasn't been proven wrong yet. We treat our laws of physics like temporary guesses that have survived every test we have thrown at them so far.

HostSo we're not standing on the truth; we're just standing on the only ideas that haven't collapsed yet.

GuestExactly. We're acting on the best hunches we have while always keeping the door open to being wrong. Science isn't a collection of settled facts about the future; it's a pile of stories about how the world works that simply haven't failed us up to this point. We're like someone walking across a frozen lake, trusting each step only because the last one didn't crack the ice.

HostThe pen still hits the floor every time I let it go, but I suppose that's just the world's way of not breaking its streak yet.

GuestThe ice is holding for now, but we have no way to prove it'll stay thick enough for the next step.

HostThe next time that pen drops, it's a reminder that we're all just betting on a habit that nature hasn't decided to break.