"A mature science is governed by a single paradigm."

“Science describes not just the observable world but also the world that lies beyond the appearances. This is a rough statement of realism with respect to science.”

“Empiricism and positivism share the common view that scientific knowledge should in some way be derived from the facts arrived at by observation.”

“Scientists are typically good at making scientific progress, but not particularly good at articulating what the progress consists of.”

“Which facts are relevant and which are not relevant to a science will be relative to the current state of development of that science.”

“A far as perception is concerned, the only things with which an observer has direct and immediate contact are his or her experiences.”

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