His biographer attributes the comparative failure of the Clavis to its inferiority in point of style, but the crudeness of his thought had quite as much to do with his failure to gain a hearing.
It seems certain that these conclusions were independent of Berkeley and Malebranche, and were not drawn from Arthur Collier's Clavis universalis (1713), with which they have much in common, but were suggested, in part at least, by Locke's doctrine of ideas, Newton's theory of colours, and Cudworth's Platonism, with all of which Edwards was early familiar.
He had believed in the prophecies of a 16th-century shoemaker poet, Bandarra, dealing with the coming of a ruler who would inaugurate an epoch of unparalleled prosperity for the church and for Portugal, and in the Quinto Imperio or Clavis Prophetarum he had endeavoured to prove the truth of his dreams from passages of Scripture.
His chief works were his translation of Grimm's Clavis Novi Testamenti (1887; revised 1889) as A Greek-English Lexicon of the New Testament, and his New Testament bibliography (1890).
He published, among other mathematical works, Clavis Mathematica, in 1631, in which he introduced new signs for certain mathematical operations (see Algebra); a treatise on navigation entitled Circles of Proportion, in 1632; works on trigonometry and dialling, and his Opuscula Mathematica, published posthumously in 1676.
The Clavis consists of two parts.
William Oughtred, a contemporary of Harriot, published an algebra, Clavis mathematicae, simultaneously with Harriot's treatise.
His chief exegetical works are his Philologisch-kritischer and historischer Kommentar fiber das Neue Testament (4 vols., 1800-1804); Philologischer Clavis fiber die Psalmen (1791); and Philologischer Clavis fiber Jesaias (1793); and particularly his Exegetisches Handbuch fiber die drei ersten Evangelien (3 vols., 1830-1833; 2nd ed., 1841-1842).
In 1712 he wrote two essays, which are still in manuscript, one on substance and accident, and the other called Clavis Philosophica.
Historia do Futuro (Lisbon, 1718; 2nd ed., ibid., 1755); this and the Quinto Imperio and the Clavis Prophetarum seem to be in essence one and the same book in different redactions.