They stem from generally held beliefs about the nature of the world and the entities found and expected therein. These presuppositions, Collingwood argued, arise from the general zeitgeist, which is a distilled product of human cognitive, social, artistic, technical and scientific endeavors of societies. They usually change slowly and not by a rational process, but the change processes are determined by complex social situations. In that sense, science in general has been dominated by a set of absolute presuppositions which might be termed materialist-localistic. Change is either completely random or has an efficient cause.
Causes are contiguous.
Those events which cannot be analyzed in terms of contiguous causes will eventually be reduced to simpler events which in turn can be analyzed in terms of contiguous causes. Surely there are more propositions which are necessary to characterize a modern scientific stance. And there are certainly many scientists who do have more complex and in some aspects differing opinions. But in a very general sense these propostions seem to be at the base of a modern scientific world view.