The commonalities between Dewey and Popper along with the depth of the probing of their scientific philosophies, alone, make their work of considerable importance in contributing to the development of a postpositivist science. Of value also are their subtle differences, which, when juxtaposed to their commonalities, add to a broad array of concepts that lend much weight to a postpositivist research design.

Conjecture and Refutation

Popper was an unabashed idealist (that is, a "metaphysical realist") in the faith he placed in humans to acquire knowledge about the world through logical reasoning, critical experimentation, and bold conjectures. He argued that although truth remained ever elusive, as a regulative ideal its quest provided an orientation beyond subjectivism by which to understand significant things about the world-important matters that did not depend on the perception of the thinker, but grounded in the substance of objective reality as squared by the facts. His purpose was to establish a surer sense of knowledge than available through Kantian a priori reasoning and the inductive empiricism of Hume and Locke.

Popper (1963) acknowledged as critically important the Kantian emphasis on intuition in the repudiation of the assumption that "we must begin with observations in order to derive our theories from them" (p. 256). Notwithstanding the role of intuition in setting out certain theoretical conjectures, which then direct further perception and cognition, for Popper, this Kantian baseline was an inadequate framework to ground the important work of critical reasoning needed to move from perception to knowledge. Intuition provided, rather an indispensable orientation, "an almost poetic" (p. 260) source of insight that helped establish a stance toward the world, but compared to scientific reasoning and critical experimentation, often wrong as a guide in the pursuit of truth, and therefore, an unreliable guide to the logic of scientific discovery. In some contrast, in Dewey`s new logic, intuition regulated by controlled inquiry in the progressive working out of a problem, remained an important guiding source of illumination all the way through the inquiry process, although with Popper, Dewey rejected intuition on its own unaided merits as a valid source of knowledge.

As with a priori reasoning, so with inductive observation, which, according to Popper also depends on a priori assumptions in the belief that general laws can be assumed from regularities that appear in experience. That supposition, according to Popper, requires a leap in inference beyond the data that violates the assumptions undergirding empirical analysis, which can capture past and present experience, but nothing definitively certain about the future. This argument does not discount an exploratory belief that posits regularities as a bold conjecture, but the mettle of any speculation needs to be tested through rigorous experimentations that can exhibit the capacity of withstanding severe testing both on the grounds of logical reasoning and relevant data analysis. More fundamentally, Popper (1963) argued that the truth of any scientific theory cannot be proven in "that we have no criterion of truth" even as we are "guided by the idea of truth as a regulative principle" (italics in original). However, to the degree that a theory withstands critical testing, solves problems in earlier relevant theories, and adds new important knowledge not previously encapsulated, it can be relied on in moving the enterprise of scientific knowledge forward even as the theory may be ultimately be proven false. In this respect, "there are criteria of progress" in achieving approximations "toward the truth" (p. 306).