[In 1692 Bayle composed an essay to support his project for a critical encyclopaedia. It would aim, he said, to rectify the mistakes he had found in Moréri's dictionary. He addressed his proposal to Jacques du Rondel, a former colleague at Sedan, who had become professor of belles lettres at the university of Maestricht. The ‘Project’ shows that the idea of a dictionary of errors arises from Bayle's approach to scientific discovery; and from his perception that an accurate historical fact could serve to negate a false conjecture. For the scholar – whether historian or natural scientist – by being alert to evidence of mistakes in received thinking could often get nearer to the truth. Perhaps the essay inspired Mill's thoughts on poetry and pushpin: Bayle – citing the poet Malherbe's ironic rebuke – asks if the good poet should be thought less useful to the state than the good player at ninepins (p. 8).]