It is system of data-based explanation that distinguishes science from dogma. (McCain & Segal, 1988, p. 38) * In a recent issue of Exceptional Children, Heshusius (1991) advocates holistic/constructivist (H/C) approaches to assessment (and instruction) in special education, as alternatives to mechanistic/newtonian approaches, ostensibly exemplified most prototypically by direct instruction (DI) and curriculum-based assessment and curriculum-based measurement (CBA/CBM). We are responding to that article on behalf of DI. What is most interesting about Heshusius' critical reflections is not her personal views of instruction and valid instructional assessment, but rather, her elaborate attempt to create impression that there is uncontested, authoritative philosophical support for her preferred alternatives. To be sure, paradigm wars wage on, but few solid conclusions have yet emerged. (See Miller & Fredericks, 1991, for a recent discussion, including a critique of Heshusius' views on ontological-methodological distinctions.) In her campaign to discredit empiricism in education, Heshusius dichotomizes world as mechanistic-Newtonian-positivist on one hand and holistic/social constructivist on other. We find little evidence among philosophers of science or scientists for implication that a rejection of mechanism and positivism requires a rejection of empiricism. In fact, we need not look further than some of Heshusius' own citations (von Bertalanffy, 1968; Bronowski, 1965) for views differing from her own. Postmechanistic science, rather, appears to embrace a more sophisticated view of empiricism and scientific method. The development of empirical methodologies for dealing with multivariance, for example, arose from inability of classical physics/mechanism to adequately describe complexities inherent in study of biology. Those same methodologies have more recently been applied to complexities of social science. (See von Bertalanffy, 1968, pp. 92-93.) Another authority cited by Heshusius, Bronowski 1965), says, Logic and experiment are locked together in scientific method, in a constant to and fro in which each follows other (p. 44). Bronowski specifically contrasts modem and mechanistic science when he describes modem science as a process, exploration of likenesses; and this has sadly tiptoed out of mechanical worlds of positivists and operationalists, and left them empty (p. 48). Ironically, exploration of likenesses is at heart of DI, as clearly explicated in another source Heshusius cites (Engelmann & Carnine, 1982). Further, Bronowski points out that step in development of scientific theory that precedes creative exploration of likenesses is collection of data, stuff' from which likenesses are extracted. Von Bertalanffy (also cited by Heshusius, see pp. 100-101) discusses two types of empiricism quite explicitly: (a) one-sided empiricism (akin to blind empiricism Heshusius rightfully eschews), in which data are merely accumulated in absence of theory; and (b) theory without experimentation-conceptual experimentation-which on Bertalanffy characterizes, crediting Kant, as intellectual When Heshusius (1986) speaks of positivist and empiricist traditions as profoundly inadequate (p. 25), she erroneously equates modem empiricism with antiquated and discredited philosophies of science (mechanism) or schools of philosophy (positivism) and, therefore, attempts to reject modem empiricism as principle means by which theoretical inquiry moves beyond mere intellectual play. Not only do some of authorities cited by Heshusius clearly support thoughtful application of modem scientific method, but they support specific instructional practices renounced by Heshusius as well. Of all tired educational aphorisms, weariest might be, the whole is more than sum of parts, which von Bertalanffy refers to as somewhat mystical. …