 In the eighteenth and nineteenth century the opponents of mechanism were typically referred to as vitalists. The various vitalists all rejected mechanism, taken as the view that organisms are composed of physical parts that operate in accord with the same principles as processes in the non-living world. Their positive views varied. Some vitalists adopted a position much like that of substance dualists with respect to the mind, arguing that some non-material component—a vital force (vis vitalis)—operates in living beings and accounts for their distinctive activities. Others avoided positing an extra component but maintained that different laws apply in living organisms than in non-living systems (for discussions of these different versions of vitalism, see contributions in Normandin &amp; Wolfe 2013). Regardless of how they expressed their positive views, vitalists commonly pointed to activities of living organisms that they claimed could not be accounted for in the same manner as physical processes. This is well illustrated in Bichat (1805), who focused first on the apparent lack of determinism in the behavior of biological organisms and second on the fact that organisms seemed to oppose physical processes that threatened to destroy them (in his words, they resist death). As noted above, Schwann and Pasteur both claimed that living yeast are needed to produce fermentation. While for Schwann this only entailed that fermentation depended on the specific combination of materials found in cells, for vitalists it entailed that living cells perform activities that could not be performed by the collection of component molecules. Bichat and Pasteur, as well as other prominent vitalists such as Müller (1837–1840), embraced empirical and experimental research, but drew limits with respect to what could be explained by appeal to the material components of an organism alone.