Lately I´ve been reading Poppers "Logic of Scientific Discovery" and I am especially interested in his critics of induction as a scientific method. When he trys to show that a principle of induction can´t be formulated, he writes:

Kant tried to force his way out of this difficulty by taking the principle of induction (which he formulated as the ‘principle of universal causation’) to be ‘a priori valid’. But I do not think that his ingenious attempt to provide an a priori justification for synthetic statements was successful.

(Popper, LoSD, P. 5-6.)

Answers I am looking for would be of the kind: Popper does this, because as you can read here (insert cool link) the approach of Kant to formulate a priori synthetic statements failed.

Or: Popper does this, because he is a whatever-ist. Whatever-ists think that there are no a priori synthetic statements. Though you should take a look here (cool link again), to see why that may be wrong/stupid/outdated.

Or finally: Popper just wanted his argumentation to work, so he had to say there are no apriori synthetic statements. In fact, those statements can be done, just follow this cool link.

4 Answers 4


Popper described his rejection of the Kantian a priori here.

A reply from a Kantian perspective can be found in this student paper.

  • Thank you, especially the student paper was a great help :)
    – Lukas
    Commented Sep 23, 2012 at 13:19
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    I would also include Chomsky's work on innate language for additional refutation of Popper's assertions.
    – Michael
    Commented Dec 6, 2013 at 18:45
  • A quick google search didnt help, could you be a little more precise as to where he refutes Popper?
    – Lukas
    Commented Dec 6, 2013 at 19:36
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    @Lukas, Chomsky does not specifically address Popper. However, Chomsky proves the existence of Universal Grammar, a kind of apriori meta-language that cannot be learned synthetically. The existence of the innate Universal Grammar, which of course includes apriori expectation of patterns and causation, refutes Popper.
    – Michael
    Commented Dec 7, 2013 at 1:07
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    It is better to cite Chapter and section numbers than pages since the pagination can be different in different issues of books by Routledge. The relevant chapter of "Conjectures and Refutations" is Chapter 2.
    – alanf
    Commented Jun 8, 2015 at 9:21

Popper took Kant's transcendental deduction of the categories seriously, but claimed that it "proved too much". It is Popper's contention that Kant, like everyone else at the time, took Newton's theory to be true, and that his transcendental deduction results in Newton's theory, or made its discovery a certainty. That Newton's theory is certainly not the only theory accounting for, e.g. gravitation, (we now have Einstein's theory), shows that our mental equipment is not bound to discover true theories.


Popper did not deny synthetic a priori knowledge because of the synthetic claim. He rejected Kant's conception of the apriori (which was knowledge thatwas valid without question). In fact in his book 'Objective Knowledge' he says that all knowledge is a priori in two senses. 1. it is logically priori to experience (ie in order to understand our experiences we already have to have in built expectations about what certain data from experience means) and second that some knowledge is genetically prior to experience (ie innate expectations we get by being part of a particular struggle for survival). It is very easy to misunderstand popper if you do not understand his weakening of the a priori. He was not saying a priori synthetic knowledge was dogmatic (as this student paper tries to argue). He was saying that claiming that some knowledge is a priori VALID is dogmatic and there is no way that you can save induction by saying that it is apriori VALID, it cannot even be a priori in Popper's weaker sense. Kant made apriori knowledge too strong and therefore made it necessary that Newton must have been correct (which is way too strong, because scientific theories are contingent).


Humans do not discover theories, according to Popper, we create them through guesswork and criticism.

The understanding of Popper is woeful. Even Chomsky, who is usually very careful in his analysis just dismisses Popper's views on language without really understanding them.

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    Do you have any references for your claims? And, although broadly correct, this does not really provide an answer to the question.
    – Philip Klöcking
    Commented Jan 28, 2017 at 17:47

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