 The introduction noted that, if the genotype-phenotype relationship had been the focus of this entry, more attention would need to be given to philosophical arguments about causality and about abstraction as it relates to causal claims. Yet, realizing any of the programs of reintegration mentioned in this entry would entail rich causal analyses: networks of gene regulation linked to organized structures that branch into more organized structures, epigenetic modifications during and across lifespans, organisms shaping the dynamics of the ecological context in which they develop their traits, and frequencies of traits changing in populations over generations. This said, in realms of experimentally controlled biological materials and conditions, a simpler sense of causality may seem plausible, namely, a difference that makes a difference (see entry on  causation and manipulability).  (The serious debate about whether statistical analysis can distinguish causal from non-causal differences that “make” a difference should be noted; Hernán et al. 2002.) The connection between an association within some population and causal mechanisms is susceptible to disconfirmation by experiments. At the same time, doing such experiments invites scrutiny of the relationship of experimentally altered dynamics to the original dynamics that generated the data that were analyzed to show the original statistical association (Taylor 2015). 