Journal of Theological Studies 17 (1916) pp. 170-1.


Has any one noticed a curious affinity between Tertullian's famous paradox and a passage in Aristotle's Rhetoric?

In arguing against the docetism of Marcion, Tertullian (de Carne Christi 5) flashes out into the following epigrams : 'Natus est Dei Filius: non pudet quia pudendum est; et mortuus est Dei Filius: prorsus credibile est, quia ineptum est; et sepultus resurrexit: certum est, quia impossibile.' This is one of the most defiant paradoxes in Tertullian, one of the quick, telling sentences in which he does not hesitate to wreck the sense of words in order to make his point. He deliberately exaggerates, in order to call attention to the truth he has to convey. The phrase is often misquoted, and more often it is supposed to crystallize an irrational prejudice in his mind, as if he scorned and spurned the intelligence in religion----a supposition which will not survive any first-hand acquaintance with the writings of the African father. The odd thing is, however, that consciously or unconsciously he was following in the footsteps of that cool philosopher Aristotle. In the second book of the Rhetoric (23. 22) we find the following sentences in a discussion of the various kinds of demonstrative proof: ἄλλος ἐκ τῶν δοκούντων μὲν γίγνεσθαι ἀπίστων δέ, ὅτι οὐκ ἂν ἔδοξαν εἰ μὴ ἦν ἢ ἐγγὺς ἦν. καὶ ὅτι μᾶλλον· ἢ γὰρ τὰ ὄντα ἢ τὰ εἰκότα ὑπολαμβάνουσιν· εἰ οὖν ἄπιστον καὶ μὴ εἰκός, ἀληθὲς ἂν εἴν· οὐ γὰρ διά γε τὸ εἰκὸς καὶ πιθανὸν δοκεῖ οὕτως. It is not difficult to see how this line of argument would justify Tertullian's 'credibile quia ineptum, certum quia impossibile '.

Aristotle's point is that, with regard to incredible events which are supposed and asserted to have taken place, you may argue that they would never have been believed at all, unless they had actually occurred; such statements must be true or almost true (εἰ μὴ ἦν ἢ· ἐγγὺς ἦν). Still further. You may argue that such incredible events are all the more likely to be true, on the ground that men believe either in (a) actual facts or in (b) probabilities; hence, if a certain statement cannot be classified under (b), i. e. if it is incredible and not probable, it must represent an actual fact. The assumption is that all objects of belief are either facts or probabilities, and this disjunctive judgement involves the paradoxical conclusion that if a given assertion is ἄπιστον καὶ μὴ εἰκός, or, as Tertullian would say, impossibile, it is all the more likely to belong to the class of τὰ ὄντα.

We demur, especially in these days of war-rumours, to Aristotle's argument about this class of demonstrative enthymemes. Common |171 sense suggests that if a given statement is extremely improbable, it need not therefore be true. But Aristotle ignores the fact that the sheer incredibility of a thing is not the best proof of its reality, and the result is what Gomperz calls a disconcerting piece of dialectical audacity. We are invited to believe that if some statement is wildly improbable (a!piston, incredibile), it is more improbable still that any one should have invented it; in other words, that it would never have been made or credited, unless there had been some evidence for it, and consequently that such evidence must be strong!

Tertullian knew his Aristotle, but he was perfectly capable of striking out a similar paradox on his own account. The passage from the Rhetoric may be no more than a parallel; possibly the argument it conveys may have been current among rhetoricians. Still, I think it is not uninteresting to note how Aristotle, in a sober discussion of the topics proper to forensic debate, could for the moment take a line which the jurist Tertullian took in the glow of theological controversy. Even if it is only a curious coincidence, it serves to modify some of the sweeping inferences drawn from the De Carne Christi by some modern critics who tend to exaggerate the psychological idiosyncrasies of the author. The paradox of the certum quia impossibile remains as pointed as ever, but it should be read in the light of the fact that this African father of the Church was not the first to defy what seems to us to be an obvious axiom of historical proof.


Greek text in unicode.

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