Is Natural Law Contained in Revelation?

Can a moral proposition be both one of natural law and also one of revealed law – one contained in Christian Revelation? ¹

The question of the relation between revealed and natural law has been raised anew in a dispute between Lawrence J. Welch and myself. In defending the positions of Pope John Paul II as found in his encyclical Veritatis Splendor(1993), Welch criticises me for holding “if one knows something by faith, it then cannot be an item of natural law.”² He counters this claim by referring to both Veritatis Splendor and also the encyclical Fides et Ratio(1998) which teach that “natural law can also be known from revelation”. Indeed, “the whole moral law, including the natural law, is contained in revelation.”³

Of what importance is this question? Both Welch and I are writing within the Roman Catholic tradition, wherein lies a dispute about the scope of the authority of the magisterium (teaching authority) of the bishops of the Church, including the Bishop of Rome. Given the authoritative Catholic doctrine that the magisterium has divine authority to determine the contents of Revelation, if Welch is correct, then the magisterium has a divine commission to teach all matters of morals.

I intend to show that Welch, in following a long line of theologians, is confused about the relation of natural law to revealed law, and I hope to clarify the relation.

First I shall outline Welch's argument. Veritatis Splendor teaches that “there is a Christological basis for the claim that revelation contains the entire moral law inclusive of the moral law known from reason”. In answer to my objection that Revelation consists of truths (true propositions) known by faith, Welch says the one moral proposition (precept)⁴ can be known both by faith and also by reason, that is, the precept can be both one of natural law and also of revelation. So the fact that the precept is one of natural law does not exclude it from the content of revelation.

Welch would seem to have on his side St Thomas Aquinas who teaches that all moral precepts belong to the law of nature.⁵ Aquinas gives three examples of such precepts: Honour your father and your mother, You shall not kill, You shall not steal. “These belong to the law of nature absolutely.” Note that these are items of the Decalogue whose revelation by God is a paradigm case of divine Revelation. So, it seems, Revelation contains natural law.

This conclusion needs to be tempered by considering the opening pages of his Summa Theologiae in which St Thomas laid the foundations of the work. There Aquinas argued for the crucial distinction between revealed truth and non-revealed, between faith and reason. He wrote:

Sacred doctrine [theology] extends to things which belong to different philosophical sciences, because it considers in each the same formal aspect, namely so far as they can be known through divine revelation(ST I, 4 – my emphasis),

and

there is no reason why those things which may be learnt from philosophical science, so far as they can be known from natural reason, may not also be taught us by another science so far as they fall within revelation

(ST I, 1, ad 2- my emphasis).⁶

I shall follow him in making this distinction between revealed and non-revealed truths.

I return to the question: Is all natural law contained in Revelation? No answer is possible until the notion of “being contained” is clarified. Buried in the argument of Welch and of the pope is an ambiguity in the meaning of the term “contained”. On the one hand it means that a proposition of natural law is identical in what it says, in its propositional content, with a proposition of Revelation, for example, You must not kill. On the other hand, it means that a proposition of natural law is a proposition of Revelation in virtue of its being one of natural law. If the latter, then Revelation contains all propositions of natural law.

To end this ambiguity, let us consider the precept You shall not kill of the Decalogue, to which Pope John Paul II refers in citing St Thomas. Is it a proposition of natural law or one of Revelation? One has no idea from looking at it, that is, from grasping what it says. In order to answer the question, it is necessary to know something in addition, something about the proposition; namely, how someone knows it. If it is known without reference to God's revealing, then it is known by reason and, as such, is a proposition of natural law. If it is known by believing God who revealed it, then it is a proposition of revealed law. It is the mode of knowing that distinguishes natural from revealed.

The context of Welch's argument is the tradition of Roman Catholic theology. Almost all its theologians, including popes, have maintained, and do maintain, that natural law is that which is known by ‘the natural light of human reason’.⁷ I should like to emphasise that this a defining property; consequently, something known otherwise is not an item of natural law.

In the Thomistic tradition of epistemology, to which John Paul II subscribes,⁸ knowing is a function of reason, and reason knows moral truths in two ways:

(1) by natural reason: Natural law, therefore, is something that we ourselves naturally bring into being by the spontaneous exercise of our own intelligence as ordered to action. It is something we bring into being by our doing (what Thomas calls a quod quis agit).⁹

and

(2) by reason enlightened by faith,¹⁰ where faith is believing “not because of the intrinsic truth of the things, viewed by the natural light of reason, but because of the authority of God himself, who reveals them”, as the First Vatican Council teaches.¹¹

Note that this sort of faith is not a product of “the natural light of human reason”. So its contents (what is believed) can not include natural law. Note, further, that this faith is believing God when God reveals, and that the revealing is done by God through words and deeds –“through the law which God gave to the Chosen People, beginning with the commandments on Sinai.¹²

Given this account of the distinction between natural reason and faith, It follows that one who knows (and therefore believes) a moral proposition by natural reason is not exercising faith. So if the pope or other bishops (who constitute the magisterium of the Catholic Church) identify propositions as those of natural law and claim to know them as propositions of natural law, they know them by natural reason, not by faith.

Now we see why a truth of natural reason cannot be a revealed truth. In so far as it is known by natural reason it is not revealed. In so far as it is known by faith (“because of the authority of God revealing”) it is not known by natural reason: it is not “something that we ourselves naturally bring into being by the spontaneous exercise of our own intelligence.” Seeing that Revelation, “the deposit of faith”(depositum fidei), consists of revealed truths and of revealed truths only, it does not contain non-revealed truths of any kind, and considering that natural law consists of truths known by natural reason, and so, qua natural law, is not known by faith, the set of truths constituting natural law does not contain any revealed truths.

The confusion in many, including Welch, arises from their failure to distinguish between believing God when he speaks, and believing what God says.¹³ God's speaking in the form of assertions is Revelation –locutio Dei, according to Aquinas¹⁴– and believing what God says is faith. But I can, for example, believe the proposition contained in You shall not kill and thus believe what God says in the Decalogue, and not be believing God speaking in the Decalogue. For instance, I may never have heard of God or of the Decalogue, and yet believe the proposition.

I offer the following analogy in the hope of making the distinction clear. I can experience pain and come to know I have cancer of the bones(proposition) without my believing anyone telling me I have cancer. Similarly, when I know a moral proposition as one of natural law I am not knowing it by believing God.

On the other hand, I can know I have cancer of the bones(proposition) believing an oncologist who tells me so following, say, a bone scan; that is, I come to know by believing him. Similarly, by faith I believe God and thus know a truth when he reveals it. Note that in both cases I believe the same proposition, and it is this fact that has confused Welch and many others.

The common claim, one repeated by Welch, that, if p is a proposition of natural law and p is also revealed, then all natural law is contained in Revelation is undermined by the following consideration.

Suppose (1)p is a proposition of Buddhist law whose propositional content (what it says) is identical with the propositional content of a proposition of Christian Revelation. (2) If Welch's argument is sound, it follows that all Buddhist law is contained in Revelation. Of course the argument is worthless because (2) does not follow from (1). Why does it not follow? Because being an item of Buddhist law does not make the item one of Christian Revelation. Likewise, being an item of natural law does not make it one of Christian Revelation.

I return briefly to the important matter of ecclesiology which is the main point of contention between Welch and me, namely, the claim that the magisterium of the Catholic Church is divinely authorised to teach all natural law because it is contained in Revelation.

As I have shown, natural law is not contained in Revelation, so any claim that the magisterium has divine authority to teach natural law has to rest on some ground other than the one offered by Welch. I leave to others to discover such a ground.