One of the main obstacles to understanding the Catholic teaching on contraception is an ignorance of the relevant meaning of the concept of nature. What sense of nature is being used when one says that contraception is “contrary to nature?” An exactly parallel sense of “contrary to nature” is used in the Church’s teaching on lying. And although the teaching on lying is as obscure to many as is the teaching on contraception, I think that a comparison of the two is illuminating. The teaching on lying is particularly illuminating, because the natures of created things can in a real sense be said to be “words” of the Creator.

Natures as words

St. Thomas Aquinas follows Aristotle in using “nature” to mean a principle of change and rest that is in a thing, making that thing be what it is. So the “nature” of a tree is the principle in the tree according to which the tree grows and stops growing, stretches out toward the sun, bears fruit, and so on. Aristotle shows in the Physics that nature is directed toward a goal, toward a good, that the thing is supposed to realize. So one could define nature as a kind of direction within a thing toward a particular good that it is supposed to realize.

St. Thomas Aquinas takes this Aristotelian account and develops it further by arguing that to act for an end presupposes some kind of knowledge. So he defines nature as an impression of the Divine Reason on creatures; the nature of each thing is a kind of participation in the divine wisdom by which that thing is directed towards its end. (Cf. his Commentary on Aristotle’s Physics, lectio 14, 268.) This is the sense of nature from which natural law is derived: human beings are directed by this innate impression of divine wisdom to seek self-preservation, reproduction, friendship, knowledge of God, and so on, and to shun what is destructive of those goods. Charles De Koninck in commenting on this passage says that every nature can be called a “Divine logos … a Divine word” (On the Primacy of the Common Good, Appendix). Logos can of course mean reason as well as word and De Koninck notes that the nature of irrational things is “a substitute for intellect” (ibid.), but a nature is also a word in a much more literal sense.

God’s principle intention in creating is to manifest his own glory, and so each nature is a sign by which God leads rational creatures to a knowledge of Himself. As St. Thomas puts it:

The creatures made by God’s wisdom are related to God’s wisdom, whose signposts they are, as a man’s words are related to his wisdom, which they signify. And just as a disciple reaches an understanding of the teacher’s wisdom by the words he hears from him, so man can teach an understanding of God’s wisdom by examining the creatures He made (Commentary on 1 Corinthians, Lectio 3, 55).

Maurice Dionne thus argues that the “natural works” of God, that is the natures of natural things, are given us as “principles which permit us to discover certain divine names” (“The Grace of Mary,” 1).

That creatures are words of their Creator is in principle knowable by natural reason, but revelation deepens our understanding of this truth. All things are created through the Eternal Word, the Logos Who is the perfect expression of the Father’s knowledge of Himself. And creation reflects that Word. But rational nature is in a special sense a reflection and even an image of the Logos. Human contemplation of God is an image of the eternal generation of the Word, and human speech is a sign of the Incarnation, in which the eternal Word was manifest in the sensible world. (See John Francis Nieto’s exposition of this point in his  lecture “Nil Hoc Verbo Veritatis Verius.”)

Two ways in which an action can be contrary to nature

So natures are words of the Creator, and they make a thing to be what it is. A tree is a tree because of the sort of participation in the divine wisdom that it has, a participation that orders it to the sort of good that can be realized by a tree, and that signifies something about its creator. Similarly a human being is human because of human nature. But not only the substantial natures of things are Divine logoi— everything was made through the Word, and without the Word nothing was made. Thus human actions, which flow from human nature and are ordered to an end, can also be said to be Divine words, and to have “natures” in this sense. One can look a kind of human actions and ask, “what is the nature of this sort of act”–i.e. what is the innate ordering to a goal that this kind of act has. Thus one can look at human speech and ask: What is human speech? What makes it to be what it is and not something else? This is crucial for understanding the teaching of Humanae Vitae; in the case of sexual intercourse too one has to ask: What is the nature of this act? What is the innate order toward a good goal in it that makes it to be sexual intercourse and not something else?

It follows, then, that there can be two ways in which an action is “contrary to nature.” In one way it can be contrary to the end of human nature as a whole—this is true of any evil action, since all evil actions are against “right reason” and contrary to the final goal of the human person. But in a more particular sense something can be “contrary to nature” if it is against the particular nature of the kind of act that it is.

We can see this in the case of speech. One can sin by saying something mean or indiscreet, and this is contrary to right reason, and thus contrary to one’s nature, but it is not against the particular nature of speech. But there is one kind of sin in speech that is indeed against the nature of speech itself. As the Catechism of the Catholic Church teaches: “By its very nature, lying is to be condemned” (CCC 2485). St. Thomas argues for this position in the Summa Theologica (IIa IIae, q. 110, a. 3) through an analysis of the nature of speech. Speech is by its nature, that is its particular nature as a certain kind of act, ordered to communicate the thoughts that a person has in his mind. So, if one says something that is directly contrary to what he thinks, then he violates the nature of speech: The action is “unnatural.”

Of course, communicating the truth is not the only good that speech realizes—speech also strengthens relationships, sounds nice, and so on. But it is communicating truth that gives speech its nature—it is the primary natural end of speech from which all the others flow. Hence St. Thomas teaches that one even the so-called “friendly lie” (lying out of politeness: “you look great”), or the jocose lie (April fool’s jokes), is sinful. The whole class of actions called lies is intrinsically bad and can never be good. (Again, see Nieto, “Nil Hoc Verbo Veritatis Verius.”)

And St. Thomas teaches something precisely similar about sexual sins. He argues that there are two ways in which a sexual act can be sinful:

First, through being contrary to right reason, and this is common to all lustful vices; secondly, because, in addition, it is contrary to the natural order of the venereal act as becoming to the human race (Summa Theologica, IIa IIae, q. 154, a. 11, c).

In the first class are sins such as adultery and fornication—they are contrary to right reason, contrary to the final end of the human person, but the are not contrary to the nature of the sexual act. An act of adultery still has the nature of a sexual act. And this because it preserves the natural order toward the end of that kind of act. The primary end of sexual intercourse is reproduction. Of course sex also realizes other goods: the union of the spouses, pleasure etc. But the one that defines it, that makes it to be what it is, that gives it its nature, is reproduction. Thus adultery and fornication are not contrary to the nature of sex. But sins such as sodomy and masturbation are contrary to the nature of sex. It is not just that in doing such acts one is not intending to reproduce; it is that the kind of act one is choosing is not a reproductive kind of act all. It doesn’t have the nature of proper sex, and hence it is unnatural. It is like a lie.

Pope Paul VI teaches (and Pope St John Paul II expands on his teaching at great length) that contraception belongs to this category of acts. Contraception is not wrong because people contracepting are not intending to reproduce (however true that might be); it is wrong because it contradicts the nature, the Divine logos of the act. It  uses the faculty of generation in a way that directly frustrates the defining end of that faculty, the end that gives that faculty its nature. It is perverse because it is contrary to the nature of the faculty in the same way that lying is contrary to speech: It changes the kind of act that you are doing into a kind of act in which a faculty is used to contradict itself. As Elizabeth Anscombe puts it, “The action is not left by you as the kind of act by which life is transmitted, but is purposely rendered infertile, and so changed to another sort of act altogether” (“Contraception and Chastity”).

Thus, contraception is always sinful. It is always contradicts the impression of the Divine wisdom that is imprinted in sexual nature. This is why Paul VI speaks of contraception as contrary to the “meaning” of the conjugal act (Humanae Vitae, 13), and why St. John Paul II speaks of the language of the body: “the truth of the language of the body can be expressed only by safeguarding the procreative potential” (General Audience of November 21, 1984).

Lying is to Equivocation as Contraception is to Natural Family Planning

While lying is always sinful, it can in certain emergencies  be morally good to deceive someone by equivocation, that is, by saying something true that one's interlocutor is liable to misunderstand. A classic example: St. Athanasius, fleeing his persecutors by boat, orders his men to turn the boat around and sail straight toward the persecutors. The persecutors ask his men, “have you seen Athanasius?” And his men answer (on his orders), “yes, he is near by.” The persecutors hurry on up stream.

What is the difference between lying and equivocating in such a situation? In both cases one is intending to deceive. But in the case of a lie you are directly acting against the nature of the act of speech—it’s the wrong kind of act that you are doing. When you equivocate you are certainly not intending to communicate truth, but the act nevertheless is the right kind of act—it has the nature of true speech—even though in this case you hope it won’t succeed in communicating truth.

The case of “Natural Family Planning” (NFP) and contraception is similar. Contraception is always sinful because it doesn’t have the nature of sex; it is like a lie. But NFP is more like equivocation. In an emergency situation (for example, inability to support more children due to unjust economic structures), one does not want the sexual act to result in pregnancy. So one chooses to engage in a true sexual act, but in such a way that it will not (likely) result in pregnancy, just as Athanasius’s sailors say something true but in a way that will not communicate the truth. Thus in certain circumstances using NFP can be morally good. As Pope Paul VI teaches:

Neither the Church nor her doctrine is inconsistent when she considers it lawful for married people to take advantage of the infertile period but condemns as always unlawful the use of means which directly prevent conception, even when the reasons given for the later practice may appear to be upright and serious. In reality, these two cases are completely different. In the former the married couple rightly use a faculty provided them by nature. In the later they obstruct the natural development of the generative process (Humanae Vitae, 16).

The difficulty that many Catholics have in understanding this teaching is caused (at least in part) by the modern concept of nature, which is very different from the true one. The natural world is seen by much of post-Cartesian modernity as a kind of machine with parts acted on by blind force, rather than an order of things directed from within by impressions of the divine wisdom. In his Introduction to St. John Paul II’s series of Wednesday audiences, The Theology of the Body, Michael Waldstein has argued that one of the Pope's main points was to try to recover the traditional view of the nature on which this teaching is based. In the final audience of the series St. John Paul says that the whole series was ordered to understanding the teaching of Humanae Vitae. What he tries to show finally is that this teaching is about our very structure as creatures of God; about the impression in us of the divine wisdom.