Science is constructed out of approximations that gradually approach the truth,

Scientific theories can always be improved and are improved. That is one of the glories of science. It is the authoritarian view of the Universe that is frozen in stone and cannot be changed, so that once it is wrong, it is wrong forever.

A theory in its scientific context is not a static museum piece, but is always being extended and modified to account for new phenomena.

Scientific theories need reconstruction every now and then. If they didn't need reconstruction they would be facts, not theories.

A theory can never be proven absolutely true, therefore there is no end to scientific endeavor. A true scientific theory is always open to be disproved, and the burden of proof is continually placed on the scientist.

Science progresses by trial and error, by conjectures and refutations. Only the fittest theories survive.

Science does not aim at establishing immutable truths and eternal dogmas; its aim is to approach the truth by successive approximations, without claiming that at any stage final and complete accuracy has been achieved.

Scientific theories are distinguished from myths... in being criticizable, and... open to modifications... They can be neither verified nor probabilified.

Any physical theory is always provisional, in the sense that it is only a hypothesis: you can never prove it. No matter how many times the results of experiments agree with some theory, you can never be sure that the next time the result will not contradict the theory. On the other hand, you can disprove a theory by finding even a single observation that disagrees with the predictions of the theory. As philosopher of science Karl Popper has emphasized, a good theory is characterized by the fact that it makes a number of predictions that could in principle be disproved or falsified by observation. Each time new experiments are observed to agree with the predictions the theory survives, and our confidence in it is increased; but if ever a new observation is found to disagree, we have to abandon or modify the theory.

Science is no inexorable march to truth, mediated by the collection of objective information and the destruction of ancient superstition. Scientists, as ordinary human beings, unconsciously reflect in their theories the social and political constraints of their times.

Each piece, or part, of the whole of nature is always merely an approximation to the complete truth, or the complete truth so far as we know it. In fact, everything we know is only some kind of approximation, because we know that we do not know all the laws as yet. Therefore, things must be learned only to be unlearned again or, more likely, to be corrected. ... The test of all knowledge is experiment. Experiment is the sole judge of scientific “truth”.

To a layperson, this ebb and flow of scientific opinion, the flipflop of theory over time, the occasionally fierce and public disagreements between viewpoints, is as mystifying as it is frustrating… This isn’t a sign of science’s weakness, though, but rather its strength, always testing assumptions, making challenges, drawing new conclusions based on the latest evidence. It may err too far in one direction, then too far in the other, correcting as it goes, but every step eventually brings us all a little closer to the truth.

A theory is only as good as its assumptions. If the premises are false, the theory has no real scientific value. The only scientific criterion for judging the validity of a scientific theory is a confrontation with the data of experience.

Nowadays, however, we are much more aware of the fact that the best proof in the world is worth no more than its premises: every scientific theory is transitory and provisional, in wait for a better one, and accepted only as long as the experimental results conform to its predictions.