[On Empiricism] It is evident, on the basis of our considerations, that this appearance of success cannot in the least be regarded as a sign of truth and correspondence with nature. Quite the contrary, suspicion arises that the absence of major difficulties is a result of the decrease of empirical content brought about by the elimination of alternatives, and of facts that can be discovered with their help. In other words, the suspicion arises that this alleged success is due to the fact that the theory, when extended beyond its starting point, was turned into rigid ideology. Such Ideology is “successful” not because it agrees so well with the facts; it is successful because no facts have been specified that could constitute a test, and because some such facts have been removed. Its “success” is entirely man-made. It was decided to stick to some ideas, come what may, and the result was, quite naturally, the survival of these ideas. If now the initial decision is forgotten, or made only implicitly, for example, if it becomes common law in physics, then the survival itself will seem to constitute independent support., it will reinforce the decision, or turn it into an explicate one, and in this way close the circle. This is how empirical “evidence” may be created by a procedure which quotes as its justification the very same evidence it has Produced.
—Paul Karl Feyerabend (1975) Against Method. p.43-44