As a new century approaches it is time to re-assess the foundations on which instructional design currently rests, as well as the "mode of thinking" that it promotes. Traditional theories regarding instructional design have largely been implicitly based on out-moded eighteenth century conceptions of the physical universe (a mechanistic world view) involving certainty, determinism, and predictability. Using insights provided by 20th century science (particularly quantum theory) into the nature of knowledge, the field of instructional design should cultivate a post-mechanistic conceptual framework which would involve exploring the construction of human knowledge, explicating the use (and limitations) of Aristotelian logic, appreciating the "theory-ladenness" of observation, realizing the role of language in constructing meaning, accepting the role and impact of the observer on what is observed, and appreciating the usefulness of both the reductionist and holistic approaches. Contains 25 references. (Author/AEF)