If I ask many people, I can probably get one person to admit that they believe in something that isn’t strictly speaking scientific. It could be large parts of our universe, such as the existence of an afterlife or a soul, or it could be smaller things such as our horoscopes actually telling us information about ourselves. There are many beliefs that humans have, and it isn’t uncommon to find someone harbouring at least one of these beliefs.

That said, I find it interesting how these people respond when being prodded about their beliefs. What I usually find is that people tend to not think about the logical consequences of their beliefs. Instead, when confronted with these inconsistencies, they will simply respond with: “I didn’t say that would happen. I’m only talking about this specific thing being true.”

As Sean Carroll explains in his book, The Big Picture, people don’t want to think about the physical laws that will be violated because of their beliefs. For example, the soul is a particularly enduring belief that doesn’t get shaken easily. People will say we have a soul because each person has this certain “essence”. Unfortunately, they don’t think about the consequences a soul would have. We can probably agree that a soul interacts with the physical world through our bodies, yet there is no way our laboratory tests can detect them. This seems to be as much of an inconsistency as claiming telekinesis is possible.

Then of course, the reason people believe in a soul usually has to do with the afterlife. Therefore, the soul is supposed to exit a body when a person dies and moves (floats?) somewhere else. Once again, this is a logical inconsistency, because we cannot detect any such “particles” a soul would be made of. As Sean Carroll writes in the book, you’re perfectly capable of making the claim that we just don’t fully understand the situation. However, to say that you need to also explain how our current theories of physics that are so successful at investigating are also wrong, and how your ideas work better. Then, scientists will jump onboard with you.

As it stands, though, including any kind of particle that is supposed to encapsulate a soul would ruin many of our physical theories. And once again, that is not a bad thing. But you can’t say that a theory which predicts many phenomena about the world perfectly right is incorrect and have no other solution. You will just be ignored. You can’t change one piece of an interconnected puzzle because it doesn’t suit you, and ignore the rest. One claim affects the next, so modification must build on what has already proven successful.

This is a very important point to make. If we consider the classic example of Newton’s law of gravitation, we know that it is not as “correct” as it could be. However, the equation isn’t wrong in the sense that it doesn’t work. It does work, albeit in certain conditions (which also happens to be most conditions humans find themselves in). Therefore, Newton’s law of gravitation will always work in these settings. Carroll also points this out in his book: the law will work just as well in a millennium as it does today.

When Albert Einstein formulated his theory of general relativity, he didn’t look at Newton’s work and toss it all out. Instead, he built upon it. Said differently, one can use general relativity in a certain domain and recover what Newton found. Even though the equations were different at the outset, the latter got back to the former, and this is a very important point in science and mathematics. You can’t break logical relationships by a whim that something doesn’t “feel” right.

Let’s take a simpler example. Imagine I were to give you the points (1,5) and (2,8). I know that the line going through these two points is $y=3x+2$, which means the y-intercept is 2. However, what if someone argued with you and said that the y-intercept is actually 4, and didn’t want to listen to anyone saying otherwise?

This is an example where it is obvious that they are making a logical mistake. In mathematics, there is no wiggle room, so the inevitable conclusion when creating a line that goes through those two points is one that also goes through (0,2). You cannot argue it.

In science, it’s a bit easier to argue a proposition, but you cannot destroy a theory without recovering what has worked in it. At the very least, you have to be able to explain why what was achieved before isn’t valid.

The problem, of course, is that people aren’t directly challenging these laws. Instead, they are talking about seemingly innocent concepts, like a soul. Unfortunately, the presence of a soul would have cascading affects through physics, eventually creating the situation of our best theories being wrong.

This is why you cannot take a block out of a “building” of scientific knowledge. Every piece is important, and changing one thing can have enormous consequences on different aspects that most people won’t think about. That’s why it’s always important to question the concept someone is proposing, because often the logical implications have not been fully though through.

When a person tells you their ideas about the world, there is no need to disregard with them. If they are as misguided as you think they are, then simply interacting with the ideas will expose their weaknesses, making it unnecessary to get into a heated shouting match.