Believe me, good folks, this is not so inconsiderable a thing as many of you may think it;—you have all, I dare say, heard of the animal spirits, as how they are transfused from father to son &c. &c—and a great deal to that purpose:—Well, you may take my word, that nine parts in ten of a man's sense or his nonsense, his successes and miscarriages in this world depend upon their motions and activity, and the different tracts and trains you put them into, so that when they are once set a-going, whether right or wrong, ‘tis not a half-penny matter,—away they go cluttering like hey-go-mad; and by treading the same steps over and over again, they presently make a road of it, as plain and as smooth as a garden-walk, which, when they are once used to, the Devil himself sometimes shall not be able to drive them off it.Claims about the physical substances and the reproductive processes of human bodies underwrite presuppositions about familial identities and roles in many cultures. The claim, for example, that the male is the true parent and the female a mere receptacle becomes part of a brief for justified matricide in Aeschylus'Eumenides(657-673). Roman declaimers often take up the question of whether blood is thicker than water. A would-be adoptive father finds his attempt to adopt a young man criticised as a symptom of the disease of luxury (Sen.Con.2.1), while a foster father finds his argument for retaining his adolescent foster sons rebutted by the birth father's claim that his biological ties are more significant—even though the birth father has not seen the children since he exposed them shortly after birth (Sen.Con.9.3). Depending on the observer, the birth of twins may be viewed as a source of family pride, as evidence of the mother's adultery, or as an abomination.