"About twelve years since, not long after the author of this essay had left the schools of Medicine, he began to be dissatisfied with the common theories of respiration and the heart's motion; and as he had not met with any writer, who had given, as he thought, a just account of the vital and other involuntary motions of animals, or derived them rightly from their true source, he purposed sometime or other to write on this subject, if not for the public, at least for his own satisfaction. In pursuance of this resolution, the following essay was begun in the year 1744; and might have been finished long ago, had not the author's time been greatly taken up with more necessary business. In compiling it, he has been careful not to indulge his fancy, in wantonly framing hypotheses, but has rather endeavoured to proceed upon the surer foundations of experiment and observation. No doctrine in philosophy, which was not built on these, has ever been able to stand its ground for half a century; and the theories of Newton, and some few others of the more happy philosophers, have therefore triumphed over all objections, because they were founded on nothing else but plain facts; facts indeed, whose existence was perhaps unknown before, and whose influence is so extensive, that while they are simple and uniform in themselves, they serve as causes for explaining innumerable effects. On the other hand, in the hypothetical method of philosophising, causes are usually assigned, which not only cannot be proved to exist, but which are frequently more intricate and complex than even the effects to be explained from them. And indeed, it cannot be expected that unguided imagination should hit upon the truth, since nature has so closely concealed many of her operations, that they often elude the united efforts of genius, industry and experiment"--Book. (PsycINFO Database Record (c) 2009 APA, all rights reserved). "Physiological writers have divided the motions of animals into voluntary, involuntary, and mixed. How it comes to pass that many of our muscles are brought into contraction, not only without the concurrence of the will, but in opposition to its strongest efforts, and why most of the organs of spontaneous motion are continually agitated with alternate contractions and relaxations, of which we are in no way conscious, while the muscles of voluntary motion remain at rest, and are not contracted but in consequence of a determination of the will to that end; are questions which have occasioned no small debate among medical writers, and which as yet they are far from being agreed about. To clear up these points, is the principal design of this essay. This essay endeavours to shew, that all the spontaneous motions of animals are explicable upon the same principle, and owing to one general cause"--Introduction. (PsycINFO Database Record (c) 2009 APA, all rights reserved).
Electronic reproduction. Washington, D.C. : American Psychological Association, 2009. Available via World Wide Web. Access limited by licensing agreement. s2009 dcunns