The philosopher, Sir Karl Popper, author of The Logic of Scientific Discovery, and Conjectures and Refutations, proposed an evolutionary view of knowledge as a constant tension between present understanding, tests of that understanding, and proposals for better understanding.
As far as modern science is concerned, Karl Popper is the most influential philosopher of the 20th century, maybe of all time. Although many scientists know his name, not all are really familiar with his thinking. Here is a brief list of his key points.
1. The main goal of empirical science is to discover the Truth about nature (Popper doesn’t use a capital ‘T’ but it conveys the very large conception of truth that he has in mind).
2. However, science can never actually get to the Truth, even in principle. The Truth would have to hold for all times, all conditions, and all places in the Universe – so attaining Truth is not an option.
3. Uncertainty is therefore a defining characteristic of scientific knowledge and Popper’s philosophy takes this principle seriously: If all knowledge is fundamentally uncertain, what do we “know”? How can science make progress (as it demonstrably does)? What are reasonable grounds for taking action?
4. Scientists propose explanations that they think are true (small ‘t’ to indicate the modest, everyday kinds of truths), hypotheses, and test them “severely,” trying to see if they are actually false.
5. A severe test is one that has a good chance of finding that the hypothesis is false if it really is false. If a hypothesis is false; we reject it. If it isn’t false, we accept it as provisionally true. At any time we can test it again and maybe reject it later, but its acceptance is always provisional and, probably, temporary.
6. We want to know if the hypothesis could be false because we don’t want to hold false ideas. It’s generally easy to find a test that will produce results that should be consistent with a hypothesis, so these tests are not very informative.
7. Philosophers used to think that “induction” (or inductive reasoning) could lead to True scientific facts and, although no one really believes this today, some people still suggest that induction is a process of inferring reliable facts from regularities in nature. Popper rejects this idea, using the famous example that, no matter how many white swans you see, you can never be certain that “all swans are white,” whereas (repeatedly and reliably) observing one genuine black swan would let you reject the hypothesis that “all swans are white.” So scientists must actively look for black swans and not white ones (that’s why a black swans are featured here).
8. If a hypothesis passes a severe test then we still don’t know if it is True (we’ll never know that) but it is reasonable to feel a bit more confident about it than we did before the test. Popper says the hypothesis has been “corroborated” by the test (not “confirmed” because many people tend to think of a confirmed statement as a True one). “Corroboration” looks at past performance, which we know a lot about; “Confirmation,” (or “verification”) often implies elements of lasting truth, which we’re not justified in assuming.
9. If we need to take action, then it is perfectly reasonable to act on the basis of the best-corroborated hypothesis that we have. After all, the hypothesis was proposed as a true explanation for a phenomenon, and if its passed all the severe tests its been exposed to then there is no reason to think it is not true.
10. A fundamental distinction is between the way basic and applied science look at corroborated hypotheses. Applied science must necessarily be satisfied with the best-corroborated hypotheses when it invests millions of dollars in creating its advances. Basic science is never fully satisfied even with well-corroborated hypotheses and, even when its knowledge advances are built on them, basic science never assumes that they are unquestionably true. Basic science is always ready to re-examine and re-test even its most well-established “facts.”
11. Our scientific knowledge consists of those hypotheses that have been tested and corroborated (i.e., not found to be false); these are the “facts.”
12. Since nothing can be certain in science, even apparent falsifications may be in error. An openness to changing our minds, a willingness to consider all possibilities, is therefore a defining trait of science. “Trial and Error” is Popper’s motto.