How Do You Know the Sun Will Rise Tomorrow?

Or what if I asked you other simple questions like how do you know gravity will still work tomorrow? How do you know a pot of water will still boil when put on a hot stove? How do you know that toothpaste will still come out of the tube when you squeeze it? What if you wake up tomorrow and discover that gravity suddenly stopped working, or that water no longer boils at the same temperature, or that toothpaste doesn’t squirt out of the tube anymore? (That’d be really weird!) Again, you’d start coming up with reasons to explain the weird situation rather than question the event itself.

Of course, these scenarios seem absurd to imagine, but they draw attention to a critical question that has puzzled philosophers for centuries—why do we confidently trust that nature will work in the same way tomorrow as it does today? That is, how do we actually know that tomorrow will be like today? Stick with me in this article and you’ll see how something as routine as sunrises actually reveals amazing truths about the Creator of the heavens and the earth—the God of the Bible!

From the sophisticated scientist conducting groundbreaking experiments to the everyday parent cooking breakfast for the family, we all rely on these fundamental things in the world to behave in a reliable manner and follow consistent rules. This is what’s called the uniformity of nature, or the principle of induction, which basically means that the future will resemble/mirror the past. (Don’t let these words scare you!) In other words, it asserts that there is consistent regularity in the universe. Obviously, this principle is crucial for making successful predictions about the future and thus is essential for doing not only science but also everyday activities in our lives. Without a foundation for this principle, the very basis for science and daily life falls apart.

Without a foundation for this principle, the very basis for science and daily life falls apart.

However, the uniformity of nature2 is so deeply ingrained in us that we never stop to question why nature is so uniform. In fact, even the brightest scholars and philosophers have struggled to explain why the world is so predictable. And not just that the future reflects the past (which everyone agrees on) but why the future reflects the past. In this two-part article, we’ll explore what’s called the “problem of induction” and unpack some of the common failures from a secular worldview to solve it and how only a true biblical worldview can provide a solid foundation for inductive reasoning.

Inductive . . . What?

In a nutshell, the problem of induction concerns the reliability of inductive reasoning. Yes, I know . . . if this is the first time hearing that term, you’re probably thinking “inductive . . . what?” (It’s okay, stick with me!) In simple terms, inductive reasoning involves drawing general (big-picture) conclusions from specifics. I like to call it “bottom-up” (specific to general) reasoning. Using the classic example, if you observe 1,000 white swans, you might come to the conclusion that all swans are white. So based on the regularity of your observations, you predict that the swans you see in the future are going to be white. (Also notice that this kind of reasoning is foundational to the scientific enterprise, and the formulation of scientific laws, based on observing regularities and projecting into the future.) But of course, as you probably noticed, inductive arguments do not guarantee certainty. The possibility always exists that the next swan you see could be a black one (or some other color). Because no matter how many white swans you’ve seen, you can never be certain that all swans are white.

Note, this type of reasoning is not to be confused with deductive reasoning. It’s important to make this distinction because many people (at least the ones I usually interact with on the streets) commonly conflate the two, failing to differentiate induction from deduction. Contrary to induction, deduction can be called “top-down” (general to specific) reasoning. It’s like starting with the big picture and seeing how all the pieces fit. So while an inductive argument cannot offer absolute certainty, a deductive argument means the conclusion (pieces) logically and necessarily follows from the premises (big picture). In other words, if the premises are true, then the conclusion is certainly true. For example, sticking with our swan theme, we can use deduction to argue:

• Premise 1: All birds have feathers.
• Premise 2: Swans are birds.
• Conclusion: Therefore, swans have feathers.3

So assuming the premises (big picture) are true, we reason from the general (all birds have feathers; swans are birds) to the specific (swans have feathers). Here’s another way to think about this distinction (and how they can actually work together) in terms of the scientific enterprise: Induction aims at developing a theory, whereas deduction aims at testing a theory. For example, using induction, let’s say one day you come up with a theory that “all dogs have fleas” based on your observations of dogs:

• You observe that dog A, dog B, and dog C all have fleas (specific observations).
• You continue to observe a lot more dogs that all have fleas (pattern recognition).
• You conclude that all dogs have fleas (general conclusion).

Now, using deduction, you seek to confirm (or reject) your theory:

• You predict that every dog in your neighborhood has fleas (form hypothesis).
• You collect every dog in your neighborhood and check them for fleas (collect data).
• You discover that only half of the dogs collected have fleas (reject hypothesis).

So as a result of your study, you conclude that “all dogs have fleas” is false. Also notice that the conclusion can never be fully proven, but it can be invalidated or rejected. Hence, contrary to popular opinion, this is why scientists can never say a theory has been “proven” to be true. The best one can say is a theory is well-supported, confirmed, or validated (to a certain extent).4

And just to be clear, even though inductive methods can’t be used to prove a conclusion is certainly true, this is not to say that induction is not a useful tool—in fact, when used properly, it is very useful and forms the fundamental basis needed for science to even work!5 However, again, the problem here that needs to be addressed is not whether induction is a reliable method that works (everyone agrees that it does) but rather, the question is why.

Enter, David Hume

Before we jump further into this discussion, let’s briefly cover the history behind this “problem of induction” as it’s commonly called. When you study the history of philosophy, you will find that philosophers have had to deal with a slew of various problems. But I would argue that the problem of induction has been—and continues to be—the biggest challenge for philosophers to overcome (without a biblical worldview, of course). Secular philosophers still do not have a real answer for it!

Although the problem of induction had been around long before the famous eighteenth-century Scottish philosopher David Hume (1711–1776), he is commonly credited with formalizing/popularizing the problem and bringing it to the forefront. In a nutshell, Hume pointed out that inductive inferences depend on a key assumption—the uniformity of nature. (As a reminder, this basically assumes that nature is consistent across time and space, meaning that we observe some regularity, and based on that observed regularity, we infer what will happen in the future.) And so, Hume asked the question: How do we justify this assumption that nature is uniform? That is, Hume questioned how we can justify our belief that the future will resemble the past, such as the sun rising tomorrow. So just because you’ve seen the sun rise every day in the past, does it automatically mean the sun will rise tomorrow?

So just because you’ve seen the sun rise every day in the past, does it automatically mean the sun will rise tomorrow?

Again, most of us take these fundamental concepts for granted! For example, we all assume that gravity will work the same way tomorrow as it does today . . . right? We don’t wake up in the morning thinking, “I wonder if gravity still works today—should I brace myself for impact with the ceiling?” No, we just assume it will work! And yet, no one has actually observed what’s going to happen tomorrow. So how do we really know that tomorrow will be like today? This is the problem Hume pointed out and took to a whole new level by formally defining it and showing its implications.6

In the end, Hume basically argued that this belief is not grounded in reason or logic but rather in human habit or custom. So we just naturally expect consistent patterns to continue, which is what drives us to learn from experience. Why? Simply because we’re accustomed to them with no rational basis for this expectation, and so, the belief in something as simple as the sun rising tomorrow is rationally unjustified. Or in simpler terms, he argued that just because something has happened repeatedly in the past, such as the sun rising every morning, does not logically guarantee that it will happen in the same way in the future.7 Since then, philosophers have been forced to grapple with this problem and have struggled to provide a coherent solution, making it a central issue in modern philosophy.

What Are the Typical (Secular) Responses?

Again, Hume’s argument has left us with a serious challenge: How can we justify the assumption that tomorrow will be like today? Let me now show you some of the common secular attempts to answer this question, starting with this one (which is probably the most common I’ve heard): “It always has, so it always will” (or some variation of that answer). But notice that this creates a logical fallacy called begging the question—using past experience as the basis for assuming future uniformity means having to assume uniformity in the first place—assuming the very thing to be proved. Essentially, this argument asserts that the future will resemble the past because the past has always been like the future (notice the circularity), which doesn’t actually explain why nature is uniform.

Granted, we all agree that there’s been uniformity in the past. But why should we expect it in the future? And how does one know that—even in the past—nature was uniform? One might say “remembering” that the past was uniform, but how would we know our memory is reliable? In the end, one must assume the past was uniform to argue correctly remembering it to be uniform. It’s like saying, “I’ve never died in the past, so I assume I won’t die in the future!” See how this argument doesn’t hold up? Anytime you use past experience as a basis for what will happen in the future, you’re stuck in a circular loop—assuming that the “past” future will be like the “future” future. You’re simply assuming uniformity to justify uniformity. But that’s exactly what the argument is trying to prove!

A typical rebuttal is, “I don’t know for certain, but it’s probable the future will be like the past.” But this response doesn’t work either because probabilistic arguments still rely on the same principle—it assumes uniformity first! So we can’t justify induction purely on experiential grounds because we must always extrapolate what we’ve observed to what we haven’t observed. (Clear as mud?)

At this point, I should mention that this circular nature can be hard to grasp—because uniformity is so foundational to our thinking. It’s like breathing air every day! We need air to survive, yet we breathe all the time without even thinking about it. We just do it! So don’t be discouraged if this concept doesn’t “click” right away.

Another common response I’ve heard, especially from those in academia: “Uniformity is just a property of the universe.” In other words, they claim that matter naturally behaves in a regular way. But notice how this response doesn’t really answer the question. It might be correct, but why? Why is uniformity a property of the universe—especially given a naturalistic worldview? And how do we know uniformity is a property of the universe? At best, one could argue the universe seems to have been uniform in the past. But how do we know it will remain uniform in the future? How do we know the laws of nature won’t change tomorrow? (Again, note the circularity!) In fact, as Hume essentially argued, uniformity of nature is not logically necessary since the universe could (in theory) behave unpredictably.

Finally, I’ve noticed many people take a more pragmatic approach, saying: “I can’t really explain why there’s uniformity; it just seems to work!” Or along those same lines, I’ve also heard: “Induction is justified because it is a reliable process that tends to lead to true beliefs.” Not only does this dodge the problem entirely, but only that uniformity seems to have worked in the past—yet still doesn’t guarantee that it will work in the future. And it assumes that what has been reliable in the past will also continue to be reliable in the future—which itself is an inductive claim in need of justification!

It’s also important to note that these kinds of pragmatic answers tacitly admit that uniformity is without justification (given a secular worldview). And that’s the whole point! No one denies that there’s uniformity in nature. The point is that unless you start with a biblical worldview, you cannot rationally make sense of it.8 Remember, we can only have a guarantee that the future will be like the past if we have a good reason to assume uniformity—which I argue that only the Christian does! And yes, it’s vitally important we have a justification for this assurance because without it, we couldn’t know anything at all based on our experiences, and science would be meaningless.

No one denies that there’s uniformity in nature. The point is that unless you start with a biblical worldview, you cannot rationally make sense of it.

Again, I know that these philosophical concepts may take time to fully understand. When I first dove into these ideas, it took me a while to grasp them too. However, once you begin to understand (even just the big picture), you will be in greater awe of our all-powerful Creator God. So I encourage you to keep sticking with me for Part 2, where we’ll explore how God’s Word provides a basis for the universe being logical and orderly, thus providing a solid foundation for induction.