The Most Fundamental Unsolved Problem in All of Science and Philosophy

What is the biggest unsolved problem?

What is the biggest unsolved problem?

If you Google this question, you might find a Wikipedia page titled ‘List of unsolved problems’. There, you will find many sublists, each containing a number of open problems within its respective field. You might also ask ChatGPT, read other blogs detailing some problems, or turn to the 7 open problems (now 6) posed by the Clay Mathematics Institute, where the prize for solving any one of them is a million dollars each. But underlying all of this is a huge philosophical question, a question put forward by David Hume in 1739, known as the ‘problem of induction’. Hume makes a very interesting observation that undermines the foundations of rational thinking and our beloved scientific method. A question that has eluded scholars for around 300 years, and one that we still do not have a good answer for:

Can we justify the assumption that the future will resemble the past?

Will objects always fall to the ground when dropped?

Do you believe an object will fall to the ground when dropped? Of course, it would; what sort of question is this? We’ve all experienced gravity. True, and I’m sure if you drop something right now, it will fall to the ground; I have no doubt about that. But why? For Hume, the answer was not so obvious, and rightfully so. Think about it: why do you believe that dropping an object will lead to it falling? Well, because of gravity, of course. Fine, but why do you believe that the force of gravity will act on the object when dropped? Well, because every time I’ve dropped something, it has always been pulled down by gravity, and thus I can establish it as a law of nature. The whole basis of you believing that gravity will act on an object once released is based on past observation(s). But this was the problem Hume pointed out. All your inferences rely, directly or indirectly, on a rationally unfounded premise that the future will resemble the past. The basis of the inference that an object will fall to the ground when released is only justifiable if you assume the future ‘must’ resemble the past, but how is the assumption itself justified? Stating that the future has always resembled the past and thus will again is a logical fallacy, a circular argument. You are assuming what you are trying to prove. Therefore, the belief that an object will fall to the ground once dropped, simply because it has been observed in the past, is rationally unjustified. We can extend this argument to most daily experiences or observations in life. Why do you think you will feel heat when you place your hand next to a fire? The same argument applies: I’ve always felt heat when I placed my hand next to a fire, and I expect the same reaction. Perhaps you are beginning to gain more intuition about the problem. Every action we take, from turning on a light and cooking food to planting seeds or using technology, is predicated on the assumption, ingrained through past experiences, that future outcomes will mirror those we’ve encountered before, and for the most part, they do! Yet, we have no satisfactory answer as to why this is or should be the case, other than practicality.

Hume turned Science into a belief system

We would like to think that our scientific method is a systematic and evidence-based approach to understanding the natural world, in which truth is established based on impeccable rationality and verifiable experimentation. But it’s very hard for us to really make such a claim. The seriousness of the question Hume put forward cannot be understated, and it’s important to appreciate the fundamental implications of Hume’s argument. Let’s revisit the gravity example. Assume that tomorrow, while leaving for work, you accidentally drop your keys on the way out, but instead of falling to the ground, they fly straight up in the air for a few centimeters before falling back down. Such an anomaly would require us to accommodate this behavior by explaining it away with some other event that can maintain the consistency of the idea that gravity is a force that is always pointing down and causes things to fall. Astronomers then come out and claim that every 3 million years, an asteroid so big with a massive electromagnetic field passes by Earth and it is close enough to cause some disturbance (I know this is not possible, but bear with me here). But what if something even more ridiculous happens? The sun suddenly starts rising in the west. Well, now we have a much bigger problem. This is not an anomaly anymore. The sun has been rising in the west for a week now! ‘Impossible’, astronomers say. They pull up all their mathematical theories and prove to you why it should always rise in the east based on the rotation of Earth relative to the sun and our galaxy. But the fundamental problem is that our theory is based on two things: historical data such as, the rotations and the speed of our planet, and the galaxy, and the ASSUMPTION that the behavior of our planet and the galaxy will remain relatively stable through the rest of time. With the new behavior of the sun, we suddenly need to reformat our theory and understanding of the cosmos. We will need to then develop a new theory to accommodate and explain this new behavior. Whatever we thought was ‘true’ was based on an underlying assumption that had no proper right to be there besides the fact that we literally cannot do science without it. We sit there, develop all these theories of cosmology but fail to take into account the possibility of the dynamic behaviors of the universe. We humans are only a drop in the vast life of the universe; the cosmological constant might not be so constant. Maybe it changes every 15 billion years in very unpredictable ways. What happens then to all our cosmology theories? We have developed partial differential equations for the rate of change of cancers, but what if tomorrow suddenly the rate we quantified shifts drastically?

These might all seem like ridiculous statements. However, the truth is, without the assumption that the past will resemble the future, so too are any statements about the future. Before we can assert what ought to be, it would be prudent to first understand and articulate why it should be. Bertrand Russell put this best in his book ‘The Problems of Philosophy’.

“The man who has fed the chicken every day throughout its life at last wrings its neck instead, showing that more refined views as to the uniformity of nature would have been useful to the chicken.”