Philosophy of Science (according to Karl Popper)

What is ‘science’ anyway? What defines science? Who defines science?

In school we have ‘science’ class. You do experiments following the scientific method, you have a hypothesis and do tests to either confirm or debunk the hypothesis.

Wind back a couple hundred years and science was originally called ‘natural philosophy’. It makes sense that philosophy plays a large role in the shaping of what we define as science.

This post is going to focus on Karl Popper, a thought leader of the philosophy of science in the 20th century. His ideas were a starting block for defining science, making him one of the most important philosophers of science. To him science should be testable, refutable and falsifiable.

Karl Popper. Source Flickr.


Swans. Source Pixabay

“All swans are white” Is this true? 

Don’t know until find a black swan, so it is falsifiable, can be proven wrong.

Logically this idea is represented by the inference rule modus tollens which follows the form:

            If Socrates is a god, then Socrates is immortal

              But Socrates is not immortal

              Therefore, Socrates is not a god

The first line is called a premise, so that would be our ‘theory’ and ‘prediction’ and the next two lines are proving how that if the prediction is false so is the theory. Important to note that you can’t prove the theory is true only that it is false.

Karl Poppers philosophy of science has this modus tollens logic at its core. If a scientific hypothesis can have this logic applied then it is a science, if not it is a pseudo-science. The process is a lot more complex for a scientific theory of course but follows the same structure. This falsifiability cannot be applied in practice it is just a theory, to apply this logic you need to use falsification.


To test falsification, you need a theory which is ‘testable’ to determine if it can be proven false.

For example, you see a black swan therefore all swans are not white.


Found one! Source Pixabay

Science is about falsification not confirmation of a hypothesis. Popper believed a good idea could be tested with the risk of being wrong, which lead to more knowledge than one which could not be tested but claimed to explain everything.

Essentially, we learn from our mistakes. Beliefs should change with gained knowledge, be tested and let it go if found to be unfalsifiable.

Popper valued falsification above induction/verification.

Induction and Verification:

Why was 6 afraid of 7? because 7 8 9. Why was 7 afraid of 8? Induction

Popper rejected verification since it relied on induction. We use induction in our everyday lives to make decisions from past experiences but Popper did not feel this was sufficient for the demarcation of science.

Science or Pseudo – Science?

Popper was concerned with demarcating science from pseudo-science.

For example, Einstein’s theory of general relativity to Popper was ‘proper science’: proposed in 1916 and tested in 1919 and made predictions which could be wrong. Compared to Freud’s psychoanalysis, which was applied to any circumstance to be true, Popper saw this and Marxism as ‘improper science’. They suffered from universal verification and had no chance to be proven wrong.

The field of philosophy of science is evolving and changing. Students of Popper, Imre Lakatos and Paul Feyerabend were great philosophers of science developing and diverging from the theories of Popper.

There are many great books (listed below) on this topic if you have enjoyed my brief introduction to Popper’s world of demarcation and the philosophy of science.

Recommended reading:

  • “What is this Thing Called Science?” by Alan Chalmers
  • “Nonsense on Stilts: How to Tell Science from Bunk” by Massimo Pigiucci
  • “Theory and Reality: An Introduction to the Philosophy of Science” by Peter Godfrey
  • “The Tyranny of Science” by Paul Feyerabend
  • “The Logic of Scientific Discovery” by Karl Popper

4 Responses to “Philosophy of Science (according to Karl Popper)”

  1. Emma Arrigo says:

    Hi Andre, glad you enjoyed it! String theory is a hard one as it is unfalsifiable, machines can’t reach the energies necessary to test predictions which goes against Popper’s definition of science. So some say string theory is more like a religion! I think that Poppers definition is not the end of defining science there is so much more than demarcating science from pseduo-science.

  2. Andre Chambers says:

    Great post! It makes sense that science should only be what can be falsified. I’ve heard some criticisms of some physics theories (String Theory, for example) that say they shouldn’t be considered science because they don’t make testable predictions. Do you reckon that it’s possible our universe can’t completely be explained by science as it’s defined here?

  3. Emma Arrigo says:

    Thanks for reading Emma! I think that it is felt in some areas like how sciences should be testable, repeatable and falsifiable. But some of his views I think have moved on for example his views on claiming that psychoanalysis is a pseudoscience, its not as black and white as he had hoped with his demarcation. Some of his students that I mentioned, Feyerabend and Lakatos have developed upon Popper’s philosophy of science. Feyerabend is famous for his view of waned to reject the scientific method entirely and had an anarchist view of science but was still inspired by Popper’s views.

  4. Emma Fazzino says:

    Interesting! I’m wondering what role do you think this plays in modern day scientific research?