This book is intended to offer a historical, conceptual and methodological analysis of selected iconic shifts (revolutions) in scientific belief and practice. Part I is a reexamination of The Copernican Revolution in the light of philosophical thinking about the history of science that has emerged in the last 60 years since its publication in 1959 (Kuhn I). The philosophy and historiography drawn from Part I is then sought and compared with that evident in the history of evolutionary inquiries (Part II) and genetics (Part III). Since turning my focus to the Philosophy of Biology in the early 1970's, I have sought studies in its history with the objective of articulating a theory of change and discovery with the guidance of epistemic values realized in inquiries (questioning strategies) in the physical sciences (Kleiner, 1968, 1970). Particularly evident in the three disciplines here studied are the trade-offs between those willing to sacrifice realism (ontic comprehensiveness) for mathematical fruitfulness (instrumentalism). I was surprised to learn from Rosenberg's Instrumental Biology that there was instrumentalism in biology, because wasn't it obvious that Darwinian histories (Kitcher, 1984) had to be fully realistic to be causally efficacious? in explaining phylogeny? But, of course, R.A. Fisher's fruitful program articulated in articles (1915-1921) and a book in 1930 was instrumental biology. As with Galileo, Kepler and Newton, the pursuit of the goal of enhancing the realism of mathematical models was a driver of discovery as the Copernican Revolution unfolded (Kleiner, 197?), but also as the Darwinian-Mendelian revolutions unfolded. I thus advocate a heuristic and qualified realism, not the unrealizable 'literal' realism brought up in recent philosophical debates (Laudan, 1986) Newton settles for an ontology that gives progressively epistemically accurate models only up to a point, the point at which empirical resolution is technically limited and, as we now know, causal determinativeness declines into chaos (Randall, 2014). Mendelism and evolutionary theory has a similar escalation of realism and indeterminism from linkage, adding chromosomes to the ontology (late 19th century cytology), to karyotypes and sub-karyotypes, to subpopulations emerging within genetic populations, to cells, developing biological individuals, reproductive and symbiotic groups, genes, their sequences, enzymes and theirs, regulators, enhancers and repressors, major transitions (Michod, 1999), and comparative developmental studies (Raff, 1996). Mendelian populations were initially studied with single-locus models and were, like the Laplacian Ideal, fully deterministic in their etiology (at least in Fisher's ideal infinite populations). Introducing linkage in computer models of the Mendelian reproductive cycle gives rise to chaos, where small variations of allelic fitnesses produce diverging evolutionary trajectories. The same outcome occurs with the proliferation of small Mendelian isolates, where sampling error generates sampling error and disparity among these isolates.