 The idea of reductive levels employed in our discussion suggests what may plausibly be regarded as a natural order of sciences. For this purpose, it suffices to take as ‘fundamental disciplines’ the branches corresponding to our levels. It is understandable that many of the well-known orderings of things have a rough similarity to our reductive levels, and that corresponding orderings of sciences are more or less similar to our order of 6 ‘fundamental disciplines’. (O&amp;P 1958: 28, emphasis added)