Summary of the book "The Logic of Scientific Discovery"- By Karl Popper

Key Insights in this book:

1. Deduction is preferable to induction, and scientists should work to disprove their beliefs rather than prove them.
2. It is not always logical to choose which hypotheses to believe.
3. Science only uses probability statements to a limited extent.
4. Popper disagreed with Heisenberg’s uncertainty principle.
5. Science isn’t about pursuing truth — it’s about achieving ever greater accuracy.

Why should I care? Explore a classic of scientific philosophy from the 20th century.

Imagine this In your little hometown, it's a gorgeous morning, so you've made the decision to take a quick stroll down the river. A stunning white swan swims around the closest bend while you're strolling along and enjoying the warm summer weather.

Oh, and look! Another white swan is immediately behind it!

Then another follows!

Being a ponderous, scientific type, you identify a recurring theme. These swans are all white. It's also simple to create a small theory because these are the first swans you have ever seen: they must all be white.

Then, seemingly on cue, a fourth swan appears. Surprise, it's also white. That certainly confirms it! This hypothesis is rapidly becoming reality.

But wait on, please. How do you know there won't be a black fifth swan? or rosy? Despite how uncommon that is, it is difficult to rule out that possibility.

Aw, shucks! And to think that all you were doing was taking a simple, stress-free stroll in the sunshine. You've unintentionally come across one of the trickiest philosophical problems of the twentieth century, though, as you find yourself surrounded by this alarmingly enormous number of swans.

How can we ever genuinely demonstrate that a hypothesis is true?

Fortunately, this  to The Logic of Scientific Discovery by Karl Popper, a famous work of philosophy, seeks to answer this very issue.

You're about to learn why your beliefs might not be as solid as you originally believed, whether they involve white swans or any other theories you've been fermenting on the side.

1. Deduction is preferable to induction, and scientists should work to disprove their beliefs rather than prove them.

Let's return to those swans first, then, okay.

You have a thought as you make your way back from your stroll along the river. How will you communicate to the rest of the world your amazing discovery that swans are all white?

Not too difficult, I think. The facts are on your side. You came up with a sound theory based on a small, focused sample size—four swans, which is essentially a flock. You have only ever seen white swans. Therefore, the theory that all swans are white is simply logical.

Given how airtight it is, even Popper would undoubtedly support you.

Popper is adamantly opposed to inductive reasoning, which is what this kind of reasoning amounts to. The issue is that we're trying to prove generalisations, like "All swans are white," using singular claims, like "This swan is white." Popper contends that this strategy is unsound logically. Any number of swans, including black ones, pink ones, and yellow ones, may have come swimming around the corner. That holds true whether you've seen four swans, 40 swans, or every swan you can think of. Always be prepared for a black swan.

However, let me ask you this: What would occur if a black swan did indeed appear?

That would refute the idea that all swans were white, I suppose. There is an imbalance in the logic at play here because particular claims cannot invalidate general ones, but they can do so.

That's a crucial aspect to remember when discussing deduction, Popper's favourite scientific technique.

Deduction begins with universals rather than details and explores the connections between them to see what other logical inferences can be made. For instance, you might assert that all birds have the ability to fly and that since swans are birds, you might infer that they have the same ability.

Popper argues that although it is logically sound, it need not always be true. Instead, a smart scientist would be alert to anything that contradicts their idea.

They would seek to disprove their own theories. For instance, suppose they learned about a bird that cannot fly, such as a penguin. The generalisation that all birds can fly is debunked by that unique instance.

For a scientist, that outcome ought not to be depressing but rather thrilling. It's a fascinating new development that will lead them to develop a more precise theory. Perhaps "All birds have wings" should be used in place of "All birds can fly." They'll then search far and wide for a bird without wings in an effort to refute that claim.

Falsifiability is important to Popper in this way. Even more so, it is what he refers to as the demarcation criterion: the uncomplicated truth that separates science from nonscience. He claims that a claim can only be considered scientifically valid if it has the capacity to be refuted. Otherwise, you're dealing with metaphysics, which is much more nebulous than science at all.

2. It is not always logical to choose which hypotheses to believe.

In the first place, there's nothing improper with asserting that "all swans are white." The error is to assume that this is the case just because you have spotted a few white swans in your neighbourhood river. You must acknowledge that your assertion that "All swans are white" is simply a hunch.

Even so, we're not quite out of the woods. Popper is still able to dissect that. Because you have to consider how you even came up with that theory in the first place in order to maintain it, guess or not. How did you think it would be a good idea to say that all swans were white?

Although it might seem like a simple question, that is not the case. Keep in mind that Popper vehemently opposes induction: the appearance of a few white swans does not suffice to support the generalisation. Therefore, developing a hypothesis like your swan theory or even more plausible scientific hypotheses like gravity or relativity has any logical foundation at all. Essentially, it is speculation.

According to Popper, developing a theory requires a small but crucial act of imagination as well as a leap of faith. He refers to it as psychologism, and logic cannot explain it in any way. As a result, it basically falls outside the purview of what he covers in his work: Popper is worried with the logical procedures that you subject a theory to, or all the events that take place after you've developed a hypothesis. But he gladly acknowledges that this flash of creativity is an essential first step. That's all it is, we just have to keep that in mind.

The choice of which hypotheses to believe also involves a small amount of unreasonable leap of faith. Because doing so would be inductivism, we cannot make decisions on what to accept solely based on our personal experiences; rather, we must make a choice.

It resembles the way a jury decides cases in court. It is up to the jury to decide what actually transpired in a given instance. The only things it has to base its decision on are the facts of the case as they are currently known and the law. The jury's decision is taken as gospel truth, however it's possible that they would have reached a different conclusion if fresh information had become available. Is the decision of a jury the truth? It would probably be more accurate to describe it as closely as we can.

Science therefore resembles a jury's decision in essence even though it strives for neutrality. It basically makes the best assumptions it can based on the facts at hand; it doesn't really deal in absolutes.

3. Science only uses probability statements to a limited extent.

Probability will be covered in the following section. Because it's important to consider the potential role that probability can play in our reasoning when addressing the idea that assertions can be true or incorrect.

Take a six-sided die as an illustration. Imagine that you wish to roll a six. You have a one in six chance of getting a six. Let's pretend to roll the die 600 times, shall we? You would probably have 100 sixes in all, but would it be exactly that? Probably not. You could have, instance, rolled 103 sixes instead.

Therefore, should you update your original hypothesis to reflect the fact that the likelihood of rolling a six is actually 103 out of 600? No, because our original claim was a scientifically calculated numerical probability claim rather than an experiment. The likelihood of throwing a six remains one in six, assuming the die is fair. That likelihood is completely unaffected by the preceding 600 tosses.

For Popper, the implication that probability statements cannot be refuted is significant. Maybe things would be different if we could actually roll the die an unlimited number of times, but we can't. Simply put, we can't put claims about probabilities to the test.

So what function do probabilities serve in science? Popper, the enthusiast of falsification that he is, says not much. Since they cannot be refuted, they typically serve no purpose.

The theory of Brownian movement, which describes how particles travel in a fluid, is one instance where probabilities actually play a part in theories. Since the liquid is moving somewhat randomly, certain variations from the mean results are absolutely expected. However, in a situation like that, the variation is hard-wired into the theory and becomes part of it. Overall, a theory like that can be disproven because the results would have to fall beyond the range of acceptable outcomes. Therefore, because it can be refuted, it belongs in science.

Popper also makes another point regarding probability that sheds a fascinating perspective on his ideas in general. What’s the difference, he asks, between forecasting the orbits of the planets and predicting a throw of a die?

You’d presumably argue that throwing the die is sheer chance, whereas the planets move in a predictable rhythm. But Popper believes that fact, the two cases are considerably more similar than you think.

Why? Because it’s all about initial conditions. We know the beginning conditions in which the planets move quite precisely via observations over many generations. But precisely what actions happen on inside someone’s fist as they shake a die? What are the specific qualities of the surface they’re throwing onto? Throwing a dice seems random, but only because we have such low awareness of the conditions. If we knew all that in detail, we’d be able to forecast the conclusion just as well as where Mars will be next Friday. And that would absolutely assist at a casino.

4. Popper disagreed with Heisenberg’s uncertainty principle.

There are some things, though, that we actually have no choice but to be uncertain about. At least, according to the physicist Werner Heisenberg.

In quantum mechanics, Heisenberg’s renowned uncertainty principle is all about the boundaries of what we can know. At a subatomic level, the more correctly we know where a particle is, the less accurately we know its momentum. The most famous example of this is if we simply examine a particle at the subatomic level: this creates a little exchange of energy with the particle, which modifies the way it acts.

In other words, there actually are severe boundaries on just what we can know. It’s not conceivable to continue getting more and more exact in our measurements throughout time. It’s only ever a matter of approximation.

Given what you’ve already heard about Popper’s ideas on probability, it’s simple to see why he was uncomfortable with Heisenberg’s results. Popper felt that scientists should be constantly updating their theories to make them more and more correct as they acquire more information and knowledge – but Heisenberg argues no, at a certain point it just isn’t possible.

To cut a long and confusing story short, Popper disagreed so passionately with Heisenberg’s ideas, that in The Logic of Scientific Discovery he actually presented an experiment aimed to falsify Heisenberg’s uncertainty principle. But Popper’s initiatives came in for criticism too, particularly from Albert Einstein. And, in later editions of his book, he adjusted his viewpoint on this.

It’s odd, actually, when you stop to think about it — from one perspective, Popper and Heisenberg aren’t so far off. What they have in common is an acceptance that it’s essentially impossible to know anything with 100 percent confidence. It’s only that, whereas for Heisenberg that sets a limit on what scientists may aspire to achieve, Popper thinks scientists should never cease in their search for ever-greater accuracy.

5. Science isn’t about pursuing truth — it’s about achieving ever greater accuracy.

For this last portion, let’s zoom out a little, and think about what Popper’s theories truly mean. And let’s forget about swans this time - I think you’ve got the picture with those. So, here’s another scenario for you.

Let’s assume, tomorrow morning, the sun doesn’t rise. It just stays dark all day. We’re presuming, for the purposes of argument, that you don’t live in the Arctic circle where this is genuinely conceivable — just suppose something happens that’s utterly out of line with what you’d expect of the natural world.

Assuming all the scientists manage to find their way to the lab, what should they do?

It wouldn’t be enough just to explain why, in this one case, the sun hadn’t risen. The scientists would have to go right back to the drawing board and change all their previous theories about the way the world works in order to account for this one day’s odd events.

They’d need to establish new scientific laws that described not only the present but the history too - new laws that fit with all the information they had accessible.

That one day when the sun didn’t rise would be enough to disprove our existing scientific ideas. But recall, even once the scientists had made the required modifications and come up with more accurate theories, every day that the sun either did or didn’t rise in accordance with those theories wouldn’t prove those theories to be true - because it would be inductive reasoning.

What those days would do is support the hypotheses – but that’s far weaker. It’s effectively just arguing that there wouldn’t be any need for the scientists to be concerned.

The moral of the story is that science is always uncertain and tentative. Science isn’t knowledge. It isn’t true. It’s just as close as we can get to it. And when we find a result that falsifies what we think we already know, that’s something to get excited about — because it suggests we can come up with new hypotheses that are ever so slightly better.

What then is the purpose of science? It's not to find the whole truth, which is impossible. And after all, there's always a chance that a black swan will appear gliding down that river or that tomorrow won't see the sun rise, in which case we'll have to start over and reevaluate our hypotheses.

Science's main goal is to simply get more precise over time while also improving.

Final thoughts

You just listened to our insights to Karl Popper's The Logic of Scientific Discovery.

These insights' main takeaway is that scientists should work to disprove their beliefs rather than confirm them. By doing this, they can update and improve their hypotheses. It is erroneous to believe that science will ever learn the complete truth about how the world functions. Every time we learn anything new, our goal should be to just get a little bit better.

Here is some fast, practical suggestions you may use to put this into practise in your day-to-day life:

Lie about your own beliefs.

Popper focuses on difficult-to-understand technical subjects like quantum mechanics, but what he truly discusses is a mentality that can also be used in much less formal settings.

Therefore, the next time you create an opinion about something, whether you're reading Twitter or listening to a podcast, look for information that refutes it rather than proof that supports it. In this way, you'll be interested in something that challenges your views and encourages you to develop a better, more inclusive worldview rather than feeling excited when you see yet another tweet that validates what you already believe.

I appreciate you listening so much. Additionally, if you can, give us a rating. The "Rate It" button can be found on your screen right now. We value your comments. Until the next insight, take care.