The fact that the regions of nature actually covered by known laws are few and fragmentary is concealed by the natural tendency to crowd our experience into those particular regions and to leave the others to themselves. We seek out those parts that are known and familiar and avoid those that are unknown and unfamiliar. This is simply what is called 'Applied Science.'
The material universe must consist ... of bodies ... such that each of them exercises its own separate, independent, and invariable effect, a change of the total state being compounded of a number of separate changes each of which is solely due to a separate portion of the preceding state.
The first thing the reasonable man must do is to be content with a very little knowledge and a very great deal of ignorance. The second thing he must do is to make the utmost possible use of the knowledge he has and not waste his energy crying for the moon. The third thing he must do is try and see clearly where his knowledge ends and his ignorance begins.
But it seems to me equally obvious that the orderliness is not all-pervasive. There are streaks of order to be found among the chaos, and the nature of scientific method is to seek these out and to stick to them when found and to reject or neglect the chaos. It is obvious that we have succeeded in finding some order in nature, but this fact in itself does not prove anything farther.
That our knowledge only illuminates a small corner of the Universe, that it is incomplete, approximate, tentative and merely probable need not concert us. It is genuine nevertheless. Physical science stands as one of the great achievements of the human spirit.