The sources considered in Christian ethics are nearly uniform among Christian ethicists. The most common version of the four-part theme is: Scripture, tradition, reason, and experience. In general, I agree with this “quadrilateral” structure, but I prefer Margaret Farley's less catchy but more precise phrasing of: Scripture, tradition, secular disciplines of knowledge, and contemporary experience. Secular disciplines of knowledge refers mainly to the sciences, both “hard” and “soft,” as well as philosophy. I believe this is a better description than “reason.” Reason, after all, is present regardless of which side of the quadrilateral one is engaging.
I would, however, expand these four common sources and add moral discernment as a fifth source because “Scripture, tradition, reason, and experience [are] only the beginning of deliberation. Deliberation becomes incarnate as Christian communities read and speak, listen and pray” (Martha Ellen Stortz). From a Christian ethical perspective, the ability of God to continue to speak to us should not be denied. One could argue that the living word of God continues to be present through the four common sources, but I believe placing an emphasis on a fifth source of discernment gives the Spirit the place to truly work God's will among us. Considering moral discernment as it's own source also makes available perspectives and concepts that would not be easily visible if considering just the four common sources. If “reason” could be considered the work of the human mind, moral discernment could be considered the work of the Spirit within humanity.
The importance of moral discernment should not be minimized. Many authors stress its significance. Lutheran ethicist Karen Bloomquist has pointed out that the differences of opinion in corporate moral discernment “can give rise to a moral outlook, a common moral substance that emerges through interactions in which our perspectives are enlarged and we ourselves are transformed.” Here I emphasize the latent aspect that Bloomquist mentions. The moral substance that is brought out and the personal transformation that takes place were in a sense always present, yet needed to be uncovered through dialogue. Because of its ability to bring these new insights to light, I believe moral discernment should take its place alongside the four common sources and not be relegated to simply “what we do with” those sources.
The work of the Spirit in moral discernment does not need to be limited to corporate dialogue either. James Nelson points out its personal nature in a slightly more academic sense when stating that “the writer does not write out of having found an answer to the problem, but rather out of having discovered the problem and wanting a solution. And the solution is not a resolution of the problem so much as a deeper and wider consciousness of the issue to which we are carried by virtue of having wrestled with that problem.” Experience itself teaches us that discernment, whether individual or corporate, brings out ideas and solutions that were inconceivable before. The place for moral discernment also has a distinctly Pauline air to it. It was Paul who stated “not that we are competent of ourselves to claim anything as coming from us; our competence is from God, who has made us competent to be ministers of a new covenant, not of letter but of spirit; for the letter kills, but the Spirit gives life” (2 Cor. 3:5-6).