Chaim Perelman resuscitated the rhetorical tradition by developing an elegant and detailed theory of argumentation. Rejecting the single-minded Cartesian focus on rational truth, Perelman recovered the ancient wisdom that we can argue reasonably about matters that admit only of probability. From this one would conclude that Perelman’s argumentation theory is inalterably opposed to natural law, and therefore that I would have done better to have written an article titled “Perelman’s Th eory of Argumentation as a Rejection of Natural Law.”
However, my thesis is precisely that Perelman’s theory of argumentation connects to the natural law tradition in interesting and productive ways. Perelman referred to natural law in a number of his essays as an example of the excessively rational focus that he sought to correct with his theory of argumentation, but he also noted the power of natural law claims in legal argumentation. To my knowledge, he never offered a detailed account of the connections between his theory of argumentation and natural law. However, Perelman’s deep and abiding concern with justice suggests that he could not help but be interested in lines of argumentation that challenge positive laws from some other standpoint— that, in some manner, he must embrace some elements of the natural law tradition.
43(4) Philosophy and Rhetoric 383 (2010)
Mootz, Francis J. III, "Perelman's Theory of Argumentation and Natural Law" (2010). Scholarly Works. Paper 86.