Before a detailed study of Tertullian's arguments may proceed, it is wise to consider his reputation as the enemy of argument and the apostle of unreason. There are two famous passages where Tertullian seems to reject argument and reason: ‘What has Athens to do with Jerusalem?’ (praescr. 7.9) and ‘it is credible because inept… certain because impossible’ (carn. 5.4). The first is a puzzle because in the Stoic Tertullian Athens has a lot to do with Jerusalem; the second is a paradox because credibility and ineptness, certainty and impossibility are opposites. These two claims have become slogans in fideist alternatives to the Enlightenment where they have each acquired a meaning which is foreign to Tertullian. Analysis of Tertullian's text will show that both puzzle and paradox make good sense, and that Tertullian's explict claim to follow the discipline of reason (disciplina rationis) and his demand ‘here again I must have reasons’ are amply justified. The first may be called ‘the puzzle’ and the second ‘the paradox’. Tertullian has countless paradoxes but this one is celebrated.

One by one the common opinions concerning Tertullian have fallen. Barnes has shown the improbability of his being the jurist Tertullian, the son of a centurion, or a priest. Hallonsten has shown that his accounts of satisfaction and merit do not anticipate later legalism. Rankin has challenged the view that he was a schismatic. It is equally necessary to show that Tertullian was not a fideist.