In summary, then, this discussion indicates one of the ways in which Simpson participated in the “modern evolutionary synthesis” by focusing on his developing concept of the species. In particular, we see him moving from species-as-types to species-as-populations, and next to how those populations, through organism-environment interactions, might give rise to new species, some of which rapidly lead to higher taxa. Simpson's participation in the creation of the modern synthesis is more generally evident here by his contribution to what V. B. Smocovitis has recently termed the “quantification of evolution — the attachment of numbers to ‘nature.’” Smocovitis rightly views such quantification as an essential ingredient for the formulation of the evolutionary synthesis; however, she neglects Simpson's role in this regard. As suggested here and demonstrated more fully elsewhere, Simpson's commitment to a positivistic philosophy often found expression in quantitative argumentation, even if the paleontological data upon which such arguments were based were limited in number and precision.