  Pascal was sympathetic to the mild, comprehensive pyrrhonism that is found in Montaigne: “Montaigne is incomparable … for disabusing those who cling to their opinions and who believe that they have found unshakeable truths in the sciences” (Entretien: II, 97). Despite this tendency towards scepticism, Pascal frequently expressed confidence in the certainty with which we can know ‘matters of fact.’ For example, he argued in the Provincial Letters that “matters of fact are proved only by the senses” and that they are “easily decided” (I, 812, 723). This was consistent with one of the main lines of argument in the Letters. Pascal's defence of Arnauld hinged on the claim that the five propositions condemned by the Pope as heretical did not occur in the text of Augustinus, and that this fact could be established easily by inspection, i.e. by reading the book. On questions of fact, therefore, even the Pope (who, Pascal accepted, was an authoritative teacher of revealed truths) could be mistaken, and it is inappropriate to appeal to any authority apart from one's senses to decide a factual question: ‘authority is useless in that context’ (Preface to the Traité du vide: I, 452). The same kind of certainty about experimental facts, he thought, should have resolved the dispute about heliocentrisim that led to Galileo's house arrest. “It was in vain” therefore that the Jesuits “obtained from Rome a decree against Galileo … That is not what will prove that the earth does not move; and if one had unchanging observations that proved that the earth revolves, all the men in the world could not stop it moving” (Provincial Letters: I, 813).