In some of my reading lately, a connection occurred to me of the sort that is so obvious once consciously realized that you feel almost idiotic for not making the linkage before. G. K. Chesterton considered logic to be a tool, an instrument of reason to be used only in service of the truth. He writes,

The relations of logic to truth depend, then, not upon its perfection as logic, but upon certain pre-logical faculties and certain pre-logical discoveries, upon the possession of those faculties, upon the power of making those discoveries. If a man starts with certain assumptions, he may be a good logician and a good citizen, a wise man, a successful figure. If he starts with certain other assumptions, he may be an equally good logician and a bankrupt, a criminal, a raving lunatic.

In this Chesterton is emphasizing the importance of first principles, or principia. He summarizes it this way: “You can only find truth with logic if you have already found truth without it” (G. K. Chesterton, Daily News, Feb. 25, 1905). Taken by itself, logic alone is ambivalent, in the sense that it can be pressed into the service either of truth or of falsehood.

Dietrich Bonhoeffer makes a similar observation with regard to the natural law, understood as distinct from and not dependent on special revelation. He writes, for example in the case of the state,

But both the concept of the contents of natural law are equivocal (depending on whether this natural law is derived from certain particular data or from certain particular standards); and it therefore fails to provide an adequate basis for the state. Natural law can furnish equally cogent arguments in favour of the state which is founded on force and the state which is founded on justice, for the nation-state and for imperialism, for democracy and for dictatorship (Dietrich Bonhoeffer, “State and Church,” in Ethics, ed. Eberhard Bethge, trans. Neville Horton Smith [New York: Simon & Schuster, 1995], 334).

In this way, Chesterton and Bonhoeffer make similar cases regarding the characteristics of logic and natural law, if both are abstracted from a dependence on biblical revelation.

This connection should not really be all that surprising, as Bonhoeffer himself identifies a created or natural law with reason: “Reason—law of what is created—of what exists” (Dietrich Bonhoeffer, “On the Possibility of the Church’s Message to the World,” in Ethics, ed. Clifford J. Green, trans. Reinhard Krauss, Charles West, and Douglass Stott, vol. 6, Dietrich Bonhoeffer Works [Minneapolis: Fortress Press, 2005], 362).

All this follows a long tradition of relating natural law and reason in the Christian tradition, and is itself continuous with the contention of the Eminent Pagan, Cicero, who equates the two: “There is a true law, a right reason, conformable to nature, universal, unchangeable, eternal, mands urge us to duty, and whose prohibitions restrain us from evil” (Cicero, De Re Publica, Book III). Aquinas reiterates this connection, defining natural law as “the rational creature’s participation of the eternal law” (Summa Theologica, II.91.2).

Aquinas’ definition is cited approvingly by the Reformer Wolfgang Musculus, who says, “the lawe of nature is that light and iudgement of reason, whereby we doe discerne betwixt good and evill” (Wolfgang Musculus, Common places of Christian religion, trans. John Man [London: Henry Bynneman, 1578], 69). In this way, elements of both Protestant and Catholic natural law traditions have identified the natural law with “right reason,” picking up on the Ciceronian theme.

As Chesterton notes, the “rightness” of the reason depends on the proper foundation, that is, the truth of Biblical or special revelation. It is a fundamentally Augustinian point that reason alone, without illumination, cannot reach true first principles about the existence, attributes, and character of God. This is where the discontinuity between the pagan and Christian concepts of natural e in. There is fundamental agreement about the methodology, so to speak, of natural law as “right reason,” but disagreement about the particular content of that rightness and the abilities of natural man to pursue it. For reason to be “right,” it needs the benefit of special revelation.