Journal of the History of Philosophy

Locke's Empiricism And The Postulation Of Unobservables DAVID E. SOLES WHEN IN THE "Epistle to the Reader" of An Essay Concerning Human Understanding Locke characterized himself as an underlaborer in the advancement of science, he was alluding to his role as a philosopher of science with the self-appointed task of providing epistemological foundations for the emerging empirical sciences and, given the fluid state of science at the time, this enterprise is not nearly so modest as Locke sometimes intimates.' To fully appreciate the significance of his undertaking, it must be remembered that when work on the Essay commenced, the nature of proper scientific practice was one of the most controversial topics of the age; in fact R. F. Jones has maintained that "the seventh decade of the seventeenth century witnessed the most vigorous defence ever carried on in behalf of experimental science,"' and that during this period debates over scientific discoveries were of less importance than debates over scientific method. Jones is primarily concerned with the need of seventeenth-century science to justify "the break with antiquity and the adoption of a method of direct investigation.''3 But there was more at issue than merely the break with antiquity; scientists were far from agreement upon the details of the new method. There were several alternative conceptions of the new science, most important of which were the Baconian, Galilean, and Cartesian. It is true that far too often the differences among these philosophies are over- ' John Locke, An Essay ConcerningHuman Understanding, ed. by P. H. Nidditch (Oxford, 1975), lo. Subsequent references to this work will be provided in the text and will consist of book, chapter, and section numbers. " R. F. Jones, Ancients and Moderns, (St. Louis: Washington University, 1961), 183. Ibid., 184. [~39] 34~ JOURNAL OF THE HISTORY OF PHILOSOPHY 23:3 JULY 1985 emphasized and the similarities undervalued. When this happens we get caricatures of Cartesians who believe that all the truths of science can be deduced from a few axioms clearly and distinctly perceived, Galileans appear as neo-Pythagoreans uninterested in any phenomena not reducible to mathematical formulae, and Baconians seem to believe that truth will arise spontaneously from an undifferentiated mass of experiments and observations . In point of fact, differences are largely a matter of degree and individual scientists subscribe to Baconian, Cartesian, and Galilean principles. This eclectic tendency of seventeenth-century science has been recognized for some time. Hall, for instance, in discussing the actual practices of these scientists, writes: "Their accomplishments sprang not from a common epistemology but from the interplay of a multiplicity of notions. At times both Galileo and Descartes wrote like Baconians, while on the other hand Bacon's own best exemplification of an inductive investigation--into the nature of heat--is nothing more than an instance of how one might compile a justification of a preliminary hypothesis. TM While Hall is correct in stressing the overlap and similarities in conceptions of scientific method during this period, it must not be forgotten that for the parties to the disputes the differences were more important than the similarities; as Hall, himself, notes, "the tendency of the time was to proclaim the merit of some single clue to the search for truth in science, to be found in reason, or mathematics, or experiment. ''5 For practicing scientists and philosophers of science in the seventeenth century it was still possible to believe that there was a single correct method of science. Discussions of correct scientific method thus proceeded on two levels. At one level, advocates of the new science were unanimous in their rejection of the teaching of the schools with its reliance on "the ancients"; at a second level, however, there was wide disagreement among the new scientists as to whether logical deduction, mathematical modeling, or experiment and observation ought to be emphasized in the quest for scientific truth. English intellectuals of all sorts, academicians, churchmen, scientists, and philosophers actively participated in both debates. 6 Locke plays a pivotal role in these controversies. While by the latter third 4 A. Rupert Hall, From Galileo to Newton (1963, rpt., New York: Dover Publications, 1981), 1o5-1o7. 5 Ibid., 1o5. An excellent discussion of...