— G. E. M. Anscombe
Contraception and Chastity (1975), Context: If a kind of love cannot be commanded, we can't build our moral theology of marriage on the presumption that it will be present. Its absence is sad, but this sadness exists, it is very common. We should avoid, I think, using the indicative mood for what is really a commandment like the Scout Law ("A Boy Scout is kind to animals" - it means a Boy Scout ought to be kind to animals). For if we hear: "a Christian couple grow in grace and love together" doesn't the question arise "supposing they don't?" It clears the air to substitute the bite of what is clearly a precept for the sweetness of a rosy picture. The command to a Christian couple is: "Grow in grace and love together." But a joint command can only be jointly obeyed. Suppose it isn't? Well, there remains the separate precept to each and in an irremediably unhappy marriage, one ought still to love the other, though not perhaps feeling the affection that cannot be commanded. Thus the notion of the "marriage debt" is a very necessary one, and it alone is realistic: because it makes no assumption as to the state of the affections.
Looking at the rightness of the marriage act like this will help in another way. It will prevent us from assuming that the pleasant affection which exists between a happy and congenial pair is the fulfilment of the precept of love. (It may after all only be a complacent hiving off together in a narrow love.) We ought absolutely not to give out a teaching which is flattering to the lucky, and irrelevant to the unhappy. Looked at carefully, too, such teaching is altogether too rigorist in a new direction. People who are not quite happily married, not lucky in their married life, but nevertheless have a loyalty to the bond, are not, therefore, bound to abstain from intercourse.