If a doubt is raised about a moral norm long accepted in any community, the presumption is not on the side of freedom from obligation. Rather it is on the side of tradition, since like a reasonable person, a reasonable community must accept what it is (which includes what it has been) and it will change only when it sees an adequate reason for change. Moreover, the presumption is on the side of the basic human goods, since when any one of them is at stake, the action which seems contrary to it is prima facie immoral. Thus for anyone who rightly recognizes the initiation of new human life to be a basic human good, the burden of proof in the present controversy will appear to fall on the defenders of contraception, just as for anyone who regards human life itself as a basic good, the burden of proof in the justification of warfare falls on those who seek to justify it.
(Germain G. Grisez, "Reflections on the Contraception Controversy," The American Ecclesiastical Review 152 [May 1965]: 324-32, at 330)
