 Most importantly given the framing of this entry around control and reintegration: Any experimental as well as statistical association is also conditional on the subset of the population or species studied and the situations where they are observed (Lewontin 1974b). Understanding associations and formulating manipulations based on them requires attention to what has been experimentally or, at least, statistically held constant. In other words, in controlled conditions the direction of the arrow labeled identification in Figures  2  and  3  may be reversed and given a causal connotation, but the causality is conditional on the factors, including the rest of the organism, held constant. The understanding and manipulations may well extrapolate beyond the original, controlled population and situations (and thus match the general theory summarized in  Figure 1),  but, absent an actual program of reintegration, there is no basis for assuming that they will. While Waters (2007), Tabery (2014) and others would give greater status to differences that have actually been observed to make a difference (Griffiths &amp; Stotz 2013), this entry has pointed to the control of biological materials and conditions that excludes many factors—genetic as well as environmental, structural as well as particulate—from being seen to make a difference. Ironically, if appearances are not to mislead and obscure, or be spun into speculative theories  (section 2),  the science of heredity needs methods that bring back what was abstracted away under the experimental control that made Johannsen’s original genotype-conception meaningful.