How can a theory of transmigration explain that we resemble our parents or grandparents? In Aristotle, a problem of this sort arises, because he maintains that in the process of procreation only the father provides the form, the mother being considered the material principle. How is it, then, that children are like their mother? The Neoplatonist Plotinus presented for the first time a new, revolutionary theory of procreation according to which both the mother and father contribute a set of "logoi" (reason-principles). The dominant reason-principles constitute the child's genetic material, as it were.