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But what a spectacle the succession of men’s opinions presents! There I seek the progress of the human mind, and I find virtually nothing but the history of its errors. Why is its course-which is so sure, from the very first steps, in the field of mathematical studies – so unsteady in everything else, and so apt to go astray? . . . In this slow progression of opinions and errors, . . . I fancy that I see those first leaves, those sheaths which nature has given to the newly growing stems of plants, issuing before them from the earth, and withering one by one as other sheaths come into existence, until at last the stem itself makes its appearance and is crowned with flowers and fruit – a symbol of late-emerging truth.

Turgot, Oeuvres, vol. 2 (Paris, 1844,), pp. 600-601 (‘Second discours sur les progres suc­ cessifs de l’esprit humain” ).:11 [Nlla)2]