All other knowledge is harmful to him who has not the knowledge of goodness.

[Toute autre science, est dommageable à celuy qui n’a la science de la bonté.]

Michel de Montaigne (1533–1592) French essayist

Essays, Book 1, ch. 24 (1.24), “Of Pedantry [Du pedantisme]”(1572-1578) [tr. Ives (1925), ch. 25]
    (Source)

While the original essay dates back to 1572-1578 and the first edition, this passage was added 1588–1592 for the 1595 edition. Some translators use the 1588 sequence of chapters, not the 1595, and so identify this as ch. 25.

(Source (French)). Other translations:

Each other science is prejudciall unto him that hath not the science of goodnesse.
[tr. Florio (1603)]

All other knowledge is detrimental to him who has not the science of becoming a good man.
[tr. Cotton (1686); Friswell (1868)]

All other knowledge is hurtful to him who has not the science of goodness.
[tr. Cotton/Hazlitt (1877)]

All other learning is hurtful to him who has not the knowledge of honesty and goodness.
[tr. Rector (1899)]

Any other knowledge is harmful to a man who has not the knowledge of goodness.
[tr. Frame (1943), ch. 25]

All other knowledge is harmful in a man who has no knowledge of what is good.
[tr. Screech (1987), ch. 25]