Verificationism is usually associated with the philosophy of language. However we can also see it is a way to conduct science (since science aims at the truth, and verification is supposed to be evidence that a statement is true). The problem with verificationism (or so it is commonly thought) is that some statements are “universal” in the sense that they make claims about a possibly infinite set of objects. Since it isn’t possible to verify that the statement is true for each of an infinite number of objects it seems that verification is impossible. Because of problems such as this falsification was proposed as a way to conduct scientific investigations. A scientist working under falsificationism attempts to find cases where the “universal” claim is false, and if no such counterexamples can be found the hypothesis is accepted as provisionally true. Thus under falsificationism we should test the consequences of a theory that we consider most unlikely (for example cases where it contradicts established theories) in order to make the best attempt to falsify it.
However perhaps we shouldn’t give up verificationism so easily. If we look at verificationism from the perspective of probability theory it recommends the exact same kind of investigations as falsificationism, showing that it might be a decent way of approaching a scientific investigation after all. We formalize verificationism with probability theory by treating every piece of evidence as confirming the hypothesis to a lesser of greater degree (note that the degree of confirmation is always positive, but a degree of confirmation less than one implies that the evidence is disproving the hypothesis). We figure out exactly how much more we should trust our hypothesis given the evidence we have collected by applying Bayes’ theorem. I won’t give you the full mathematical run-down, but suffice to say that in order to achieve the greatest degree of confirmation for a theory it is necessary to look for evidence that the hypothesis predicts is likely but that is considered generally to be unlikely, and as mentioned above this is the exact same recommendation that falsificationism gave us.
So if both falsificationism and verificationism endorse the same kind of investigation which one should we prefer? I personally think that verification, understood as the search for evidence with a degree of confirmation greater than one, is a superior way of looking at the scientific process. Besides encouraging us to look for evidence that is likely to falsify the theory (which proponents of falsificationism have shown to be a good idea on numerous grounds) it also provides a way to show several other intuitive ideas about science to be true. For example verificationism as interpreted here shows that you can never prove that a hypothesis to be true beyond the possibility of doubt (the probability of the hypothesis is always less than one no matter how much evidence you have), and that you cannot disprove a hypothesis unless it predicts that some events are impossible. Finally it also provides a way to judge which of two hypotheses is superior if both of them have only supporting evidence and no counterexamples (you determine which hypothesis is confirmed to a greater degree). Does this really matter to scientists? No, but it does impact how we think about epistemology.