h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I would recommend Karl Popper's "The Logic of Scientific Discovery" as essential further reading.

Popper also recognises the shaky logical foundations of Bacon's inductivism, and proceeds to establish a sound logical basis for the interpretation of scientific statements.

It follows that we can never be certain that today's scientific hypotheses aren't going to be refuted tomorrow. The conclusions are rather less pessimistic than Kuhn's. Lack of certainty does not after all imply absence of knowledge.

While scientific hypotheses should only be accepted tentatively, scientific method - the subjection of these hypotheses to reason and empirical refutation - means that we have (in my intepretation of Popper) a better reason to accept a scientific hypothesis than a similar hypothesis that is not or cannot be subject to the scientific method.

Popper also has a proof that the probability of any scientific hypothesis being true equals zero. Whether you accepts this or not, it illustrates that we can only test such ideas by their consequences. The question of whether a hypothesis is really true, rather than appearing to be true, is a metaphysical question not a scientific one.