The systematic production of usable flakes is often presented by lithic technologists as a rigid set of strategies or procedures to be followed in a step-by-step fashion. The quintessential example is the chaîne opératoire, developed by the French in the 1980s and widely applied today. An alternate view is that lithic reduction is a fluid behavioral set conditioned by an intimate familiarity with techniques and materials and tempered by environmental and situational circumstances. In an effort to address the 'how' and 'why' questions central to an epistemologically informed archaeology, and thus help lithic analysts from different research traditions better understand one another, we contrast models of discrete lithic reduction stages with those based on models of reduction continua. How we understand reduction influences how we interpret it. First, we summarize experimental data from North American bifacial reductions that can be modeled as continuous reduction processes using regression and principal components analyses. Then we apply these same methods to refitted cores from WHS 623x, an Upper Paleolithic site in west-central Jordan. The analysis shows that some aspects of lithic reduction are best modeled as continua, while others are better modeled as discrete. If reduction is continuous in some respects, it should be understood in continuous terms in those respects.This special issue is guest edited by Gilbert B. Tostevin (Department of Anthropology, University of Minnesota). This is article #4 of 7. M any archaeologists view lithic reduction as a process that unfolds in essentially discrete, generalizable stages (e.g., Boëda 1993; Boëda et al. 1990;Callahan 1979). This view has a long history and can be traced to various sources. In the Old World, with its great time depth, it is often tied to assumptions and preconceptions about hominin cognitive evolution, with the implication that biology and culture are linked in a more or less linear fashion (e.g., Grahame Clark 1969, Foley and Lahr 1994), and that lithic typology and technology tend to co-vary with one another over space and time (e.g., Bar-Yosef 1994, 2002Bordes 1961;de Sonneville and Perrot 1953). In the New World, William Henry Holmes originated the reduction-sequence concept over a century ago (Holmes 1894;Shott 2003). But the possibility that reduction might be continuous in some cases and respects, shaped only by generalizable contingencies with which all Stone Age societies must contend, has seldom been addressed. Holmes apparently shared this view. He explicitly recognized that stages were analytical constructs, not revealed entities present in the minds of people long dead:"There can really be no line of demarcation separating the phenomena of one stage from those of another and there is a danger of the change being thought of as a definite and restricted episode, as marking a complete ending of one phase of existence, and as being a datum point from which to begin the study of the succeeding phase" (Holmes 1892: 248-249, cited in M...