[1] He published his conclusions anonymously, but with the express support of Thomas van Erpe, in his book Arcanum punctuationis revelatum (Leiden, 1624).

Nearly a century earlier, Elias Levita (1469–1549) demonstrated in 1538 that neither Jerome nor the Talmud showed any acquaintance with the vowel points, a comparatively recent Jewish invention.

[3] In 1634 Cappel had already completed work on a second important work, Critica sacra: sive de variis quae in sacris Veteris Testamenti libris occurrunt lectionibus (Sacred Criticism: Variant Readings in the Books of the Old Testament), but because of the fierce opposition of his co-religionists was able to print it only in 1650, by aid of a son, who had turned Catholic (according to the Encyclopædia Britannica Eleventh Edition)[4] or (according to Michael C. Legaspi in 2010) of the Catholic priest-scholar Jean Morin.

[1] Crawford Howell Toy and Karl Heinrich Cornill state in The Jewish Encyclopedia: "It is to the lasting credit of Cappel that he was the first who dared to undertake, with exemplary clearness, penetration, and method, a purely philologic and scientific treatment of the text of the Bible.

"[7] Cappel was also the author of Annotationes et commentarii in Vetus Testamentum and other biblical works, as well as of several other treatises on Hebrew, among which are the Diatribe de veris et antiquis Ebraeorum literis (1645).