 As a sociological, not a logical matter, success in engineering may underwrite theoretical generalizing and both may, in turn, make more plausible any assumed extension to naturally varying populations. Together with further experiments, these pathways may eventually lead to success in re-integration. It could be imagined that the processes exposed in controlled conditions would eventually explain heredity in naturally varying populations. This might happen by researchers identifying the material constituents of the genotype passed to the organism by its parents and then tracing how all these constituents influence the development over time of the organism’s traits or phenotype—perhaps first in controlled conditions, and then in variable ecological situations (see entry on  reductionism in biology).  However, there is no guarantee that the original experimental basis for the genotype-phenotype distinction or subsequent developments must lead to effective engineering, theoretical generalization, or likening that clarifies. Indeed, as a sociological not logical matter, pursuing such steps may distract attention from the project of re-integration.  Section 5  reviews what would be entailed in reintegration, doing so in order to problematize the status of the original experimentally based distinction as a basis for the study of heredity for natural varying populations. The rest of section 4 points to several areas of philosophical discussions brought into play and extended by experiments followed by the pathways and steps above.