Karl Popper's philosophy of science requires us to be overly critical of scientific theories.

I'll offer a quick summary of Popper's basic theory and then give three examples of how his account of science requires us to be overly critical of scientific theories due to its narrow scope. Since some of the readers may be unfamiliar with philosophy of science I'll do my best to keep everything clear and simple and will adjust according to the nature of the debate. Popper's deductive, falsificationalist model of science. Popper limited science to a deductive model of reasoning in order to avoid the problem of induction. A scientist begins with a conjecture or hypothesis (H) that makes a falsifiable prediction of what observations (O) will be made as a result (If H then O). If the predicted outcome is not observed (not O) then the hypothesis is considered falsified (not H via modus tollens). Even if the prediction is falsified only one time out of many tests, scientists should discard the hypothesis and come up with another conjecture. If the predicted outcome is observed repeatedly this tells us nothing more than that the theory has not yet been falsified. To do so, according to deductive logic, would be a form of the fallacy called assuming the consequent: i. e. because we observe O we can assume that H is true. Although most philosophers are fallibilists in that they admit the possibility that new evidence may require us to modify or discard current theories that appear highly accurate, most of these also hold the position that we are justified in considering a theory that is reliably accurate throughout many tests to possess more support than one which has not been tested at all. Popper's theory is contrary to these other accounts that claim a theory becomes better supported the more it successfully predicts the given observation without failure. Popper rejects these theories because it is not based on deductive logic. This is why Popper claims that science can only tell us if a theory is false and is unable to provide support to a theory no matter how many times it passes our tests. The history of science has not followed falsificationalism, and it's a good thing it didn't. As I stated earlier, Popper argued that if a predicted observation fails the theory should be considered falsified and discarded. If science had followed this approach, however, the results would have been tragic. Historically, most theories have been convincingly falsified from the beginning, and do not prove themselves until much later. For example, when Copernicus developed the heliocentric theory that the earth revolved around the sun, there were serious problems that he was unable to account for. Many significant observations that his theory predicted were not observed. It wasn't until Galileo later solved these problems that the heliocentric model was able to make accurate predictions. It was due to the fact that Copernicus and others persisted with the same theory, even if its predicted observations failed, that they continued in what turned out to be the correct understanding. This story is reflected in the developments of many other theories throughout history. Rejection of probability within science. Popper uses his falsificationalism to differentiate between science and non-science (i. e. pseudo-science). A. How does his philosophy categorize measurements of probability in science? Popper requires that a theory make falsifiable predictions in order to be counted as a science. Much of science, however, deals with probabilities. Instead of making predictions that if O is not observed then H is false, theories that deal with probability state that O is likely to occur, but is possible that it might not. If O isn't observed, then this doesn't necessarily refute the hypothesis. According to Popper's philosophy, theories that deal with probabilities in this way are not logically considered science since it does not call for an absolute prediction. This, again, is an overly critical account of science as probability is an extremely effective tool in science. Popper tries to soften this outcome of his philosophy by allowing probability "in practice," but he does this only by undermining the very core of his philosophy which requires methodology to be based on deductive logic. He can not have both his ideal of what he would make the foundation of science and still account for some of the most effective parts of science. They are incompatible. Failure to differentiate theories that have reliably passed many tests from un-tested ones. By disallowing the possibility of confirmation and support Popper makes it impossible to place more confidence in a theory that has withstood repeated tests for decades or centuries. Initially, this may sound acceptable since stable theories that have withstood the test of time have later been disproven and replaced by other theories. There are serious problems with this approach, however. By denying that theories gain support and become more credible as they withstand our attempts to disprove them, well-tested theories have no more support or credibility than newly proposed theories that have never been tested. For example, imagine we are to construct a bridge. In order to go about doing this, we must determine the best design for the bridge. We would need to make use of theories that the various designs are based upon in order to choose the appropriate design. How can we determine which design is most likely best? The most rational thing is to select the design that has been subjected to the most tests and has been successfully used in other projects similar to the bridge we are building. We would choose the design that has so far demonstrated itself to be the most reliable. According to Popper's theory, however, there is no difference between a design based upon theories that have been rigorously tested and an experimental design that has never been tested before. They each have the same amount of support- none. In practical experience we are required to make choices between theories, but Popper's philosophy does not account for these situations. This is a significant problem in his theory. Conclusion. From just these three criticisms of Popper's falsificationalist account we can see that his philosophy of science is too narrow to account for the methods and processes of science. He attempts to restrict the field of science to that which is founded upon deductive logic, but this would require scientists to throw out 1) theories that may turn out to be accurate accounts of our world, 2) powerful tools used by scientists to examine the world (i. e. probability), and 3) our rational method of selecting one well-tested theory over a newly-proposed theory that has never before been tested. The only way for Popper to avoid this is to retract the very foundation of his entire theory. His theory is largely incompatible with the effective practice of science and the way we apply its discoveries. I thank the readers for their interest and look forward to my opponents reply.