popper-logic-scientific-discovery

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the logic of science
establish or justify the statements which are being tested; nor is it
intended to do so. Thus there is no danger of an infinite regress. But it
must be admitted that the situation to which I have drawn attention—
testability ad infinitum and the absence of ultimate statements which are
not in need of tests—does create a problem. For, clearly, tests cannot in
fact be carried on ad infinitum: sooner or later we have to stop. Without
discussing this problem here in detail, I only wish to point out that the
fact that the tests cannot go on for ever does not clash with my demand
that every scientific statement must be testable. For I do not demand
that every scientific statement must have in fact been tested before it is
accepted. I only demand that every such statement must be capable of
being tested; or in other words, I refuse to accept the view that there
are statements in science which we have, resignedly, to accept as true
merely because it does not seem possible, for logical reasons, to test
them.