In one respect the law is the most perplexing subject with which a man can deal. It shifts and changes so rapidly that only a nimble and diligent student can keep abreast of it. One is likely to wake up any morning and find that the legislature has repealed a good part of what he knows, and he is in constant danger of having his most carefully formed opinions completely upset by a new decision of the Supreme Court. These violent changes are not due to any new discoveries, such as constantly enliven the scientific world, but merely to the shifting sentiment of legislative bodies and to the powerful influence of a certain variable element which enters into every legal equation. The legislative innovations are in a sense extrinsic factors. But the judicial "variable," if we may use the term, is an innate condition, and every judicial opinion may be considered a function of that variable.
Sunderland, Edson R. "The Art of Legal Practice." Mich. L. Rev. 7 (1909): 397-408.