"Until quite recently, the argument presented by Christian [moralists]] against artificial birth-control has mainly been that the sexual act is naturally designed for procreation, and it is wrong to frustrate this design because it is wrong to interfere with man's natural functions. Many persons are not quite convinced by this argument, which does seem open to rather elementary objections. After all, we do interfere with other natural functions, for instance when we use ear-plugs or hold our nose, etc., and no one has ever argued that to do so is morally wrong. Why then should it be wrong to interfere for good reasons with the procreational aspect of marital intercourse?"