The problem of induction
Summary
There is no (logical) reason to believe that the “laws of nature” will continue to operate in the future.
See David Hume’s Problem of Induction.
Briefly: the idea that the past is good evidence for the future is called the principle of induction. How do we justify this principle? By observing that it’s been true in the past, and therefore will continue to be in the future. In other words, the principle of induction is itself justified via induction. This is circular reasoning, and thus invalid.
If that’s hard to follow, maybe this conversation will help:
A: The past is good evidence for the future.
B: I can see that’s been true in the past. Why do you think it will continue to be true?
A: Because it’s been true in the past.
B: And you’re assuming that means it will continue to be true?
A: I’m not assuming anything! I have evidence for it!
B: Yes, from the past. But why is that good evidence for the future?
A: Because… the past is good evidence for the future, duh!
There is no non-circular reason to treat the past as good evidence for the future. Therefore, physical law having held in the past cannot be taken as evidence that it will continue to hold in the future. This is a point easily and commonly misunderstood regarding the Problem of Induction.
It’s a good test of whether someone has actually understood Hume’s argument that they acknowledge its conclusion is fantastic (many students new to philosophy misinterpret Hume: they think his conclusion is merely that we cannot be certain what will happen tomorrow.) … [But] if Hume is right, the belief that the sun will rise tomorrow is as unjustified as the belief that a million mile wide bowl of tulips will appear over the horizon instead. We suppose the second belief is insane. But if Hume is correct, the first belief is actually no more rational. … [T]he onus is on these defenders of “common sense” to show precisely what is wrong with Hume’s argument. No one has yet succeeded in doing this (or at least no one has succeeded in convincing a majority of philosophers that they have done so).
As with the belief in the past, it may be practical to assume that laws will continue to hold, but this is different from it being justified on logical grounds. Nonetheless, your mind will continue to believe it has justified it: “well it’s worked so far, and that’s pretty good evidence!”
[Wheeler would] say things like, “In the end, the only law is that there is no law.” There’s no ultimate law of physics. All the laws of physics are mutable and that mutability itself is a principle of physics. He’d say, there’s no law of physics that hasn’t been transcended. I saw this, and I remembered my joke about how the laws of physics must be wrong, and I was immensely attracted to this idea that maybe ultimately there actually are no laws of physics. What there is in place of laws, I didn’t know. But if the laws weren’t 100 percent trustworthy, maybe there was a back door to the stars.
– Christopher Fuchs, discussing his advisor, physics titan John Archibald Wheeler.