<P> In the extreme empiricism of the neopositivists--at least before the 1930s--any genuinely synthetic assertion must be reducible to an ultimate assertion (or set of ultimate assertions) that expresses direct observations or perceptions . In later years, Carnap and Neurath abandoned this sort of phenomenalism in favor of a rational reconstruction of knowledge into the language of an objective spatio - temporal physics . That is, instead of translating sentences about physical objects into sense - data, such sentences were to be translated into so - called protocol sentences, for example, "X at location Y and at time T observes such and such ." The central theses of logical positivism (verificationism, the analytic--synthetic distinction, reductionism, etc .) came under sharp attack after World War II by thinkers such as Nelson Goodman, W.V. Quine, Hilary Putnam, Karl Popper, and Richard Rorty . By the late 1960s, it had become evident to most philosophers that the movement had pretty much run its course, though its influence is still significant among contemporary analytic philosophers such as Michael Dummett and other anti-realists . </P> <P> In the late 19th and early 20th century several forms of pragmatic philosophy arose . The ideas of pragmatism, in its various forms, developed mainly from discussions between Charles Sanders Peirce and William James when both men were at Harvard in the 1870s . James popularized the term "pragmatism", giving Peirce full credit for its patrimony, but Peirce later demurred from the tangents that the movement was taking, and redubbed what he regarded as the original idea with the name of "pragmaticism". Along with its pragmatic theory of truth, this perspective integrates the basic insights of empirical (experience - based) and rational (concept - based) thinking . </P> <P> Charles Peirce (1839--1914) was highly influential in laying the groundwork for today's empirical scientific method . Although Peirce severely criticized many elements of Descartes' peculiar brand of rationalism, he did not reject rationalism outright . Indeed, he concurred with the main ideas of rationalism, most importantly the idea that rational concepts can be meaningful and the idea that rational concepts necessarily go beyond the data given by empirical observation . In later years he even emphasized the concept - driven side of the then ongoing debate between strict empiricism and strict rationalism, in part to counterbalance the excesses to which some of his cohorts had taken pragmatism under the "data - driven" strict - empiricist view . </P> <P> Among Peirce's major contributions was to place inductive reasoning and deductive reasoning in a complementary rather than competitive mode, the latter of which had been the primary trend among the educated since David Hume wrote a century before . To this, Peirce added the concept of abductive reasoning . The combined three forms of reasoning serve as a primary conceptual foundation for the empirically based scientific method today . Peirce's approach "presupposes that (1) the objects of knowledge are real things, (2) the characters (properties) of real things do not depend on our perceptions of them, and (3) everyone who has sufficient experience of real things will agree on the truth about them . According to Peirce's doctrine of fallibilism, the conclusions of science are always tentative . The rationality of the scientific method does not depend on the certainty of its conclusions, but on its self - corrective character: by continued application of the method science can detect and correct its own mistakes, and thus eventually lead to the discovery of truth". </P>

Who is the thinker that unified the divide between empiricism and rationalism