Successful scientists have often been people with wide interests.Their originality may have derived from their diverse knowledge.Originality often consists in linking up ideas whose connection was not previously suspected.Furthermore，variety stimulates freshness of outlook whereas too constant study of a narrow field predisposes （使先倾向于）to dullness.Therefore reading ought not to be confined to the problem under investigation nor even to one’s own field of science，nor，indeed，to science alone.However，outside one’s immediate interests，in order to minimize time spent in reading，one can read for the most part superficially，relying on summaries and reviews to keep up with major developments.Unless the research worker cultivates wide interests，his knowledge may get narrower and narrower and restricted to his own specialty.One of the advantages of teaching is that it obliges the scientist to keep informed of developments in a wider field than he otherwise would.
It is more important to have a clear understanding of general principles，without，however，thinking of them as fixed laws，than to load the mind with a mass of detailed technical information which can readily be found in reference books or card indexes.For creative thinking，it is more important to see the wood than the trees；the student is in danger of being able to see only the trees.The scientist with a mature mind，who has reflected a good deal on scientific matters，has not only had time to accumulate technical details but has acquired enough perspective to see the wood.
Nothing that has been said above ought to be interpreted as depreciating（贬低）the importance of acquiring a thorough grounding in the fundamental sciences.The value to be derived from superficial and ’skim’reading over a wide field depends to a large extent on the reader having a background of knowledge which enables him quickly to assess the new work reported and grasp any significant findings.There is much truth in the saying that in science the mind of the adult can build only as high as the foundations constructed in youth will support.

In the second paragraph the author uses an analogy (类比) that assumes that general principles are similar to（）.