December 20th. Heredity and Environment are the master-influences of the organic world. These have made all of us what we are. These forces are still ceaselessly playing upon all our lives. And he who truly understands these influences; he who has decided how much to allow to each; he who can regulate new forces as they arise, or adjust them to the old, so directing them as at one moment to make them cooperate, at another to counter act one another, understands the rationale of personal development. Natural Law, p.255.