Karl Popper, Philosopher of Science

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What is his TYPE.

"I think Popper is incomparably the greatest philosopher of science that has ever been" - Sir Peter Medawar, winner of the Nobel Prize for medicine.

"My scientific life owes so much to my conversion in 1945... to Popper's teachings on the conduct of investigations... I have endeavoured to follow Popper in the formulation and in the investigation of fundamental problems in neurobiology" - John Eccles, Nobel Prizewinner.

A basic introduction to Karl Popper's general philosophy:

Lecture 1 - Values (You can probably skip this)
Lecture 2 - Scientific Method
Lecture 3 - Problems

My thesis is that science starts with problems and not with observations, and that the difference between science and unscientific myth consists primarily in the fact that some people begin to ask awkward questions about the myths. Someone, in other words, begins to criticise the myth, and out of this criticism there arise new stories, and the result of that is further criticism, and further stories, and so on. And so we get a certain history of views about the world, and the latest of these views is the so-called accepted scientific opinion.

Now, you will say, perhaps, that this is a very low view of science to take. But I happen to think that it is a very high view to take. Science, in this sense, is the result of a lot of thought and a lot of criticism. Observation does play a very important role. But it does not play the role that most people think. Our theories do not begin with observations. But we use our observations wherever we can to check them. It is, in fact, part of our criticism to check our theories against our observations. And I can check a theory against observations only if I first have a theory.

But now, some of you must be thinking, ‘Isn’t this a bit too strong? For how can you possibly have a problem if you have never observed anything?’ My answer is that a new born child may well have a problem if he is not fed, or if he is cold! And not because he has made some observations and is now trying to generalise from them, but because he has some inborn expectations that have not yet been satisfied.

Inductivists say that it is inconceivable that we should start without observations. But I would almost like to put it the other way round and say ‘It is inconceivable that we can start with observations’. My own view is that the aim of science is to explain—very simple, to explain. To explain what? To explain whatever has become a problem for us to understand.

Whenever we ask ourselves ‘Why is it so?’ or ‘Why does it happen in just this way?’, the it in these questions—whatever it may be—has for some reason become a problem for us. The aim of science is then to solve this problem by giving an explanation. And we attempt to solve these problems, in the main, by conjecture and refutation—by guess-work. Or, if you like, by trial and error.

...all that we can say is that scientists start with problems and propose theories as solutions to them, that they criticise these solutions and try to eliminate their errors, and that what we call ‘science’ are those solutions that have been criticized in a reasonably severe way and have not yet been found too badly wanting. And that is all.

In science we start from problems and we offer solutions to these problems. How do we get these solutions? We just have some idea! We cannot really explain how a man gets a new idea, though one can say a few things about it! And then, after a solution to the problem has been offered, we begin the hard work of testing it. The solution—we can call it a theory or a hypothesis, it doesn’t matter—the hypothesis is tested by criticizing it. We criticise the hypothesis and try to find out how to refute it. That is roughly the procedure in science.

...the probability of a generalisation is supposed to be the quotient obtained from dividing the number of positive instances by the total number of instances. So it all depends more or less on the size of the world. And if the world is very large, as our world is compared with the instances that we actually do observe, then this quotient, as a measure of the probability of the generalisation, will be approximately 0.

So my thesis is that probability doesn’t get you anywhere, that if you try to apply it you get probabilities indistinguishable from 0 for well-established natural laws, instead of getting probabilities approaching 1.