The two decades of retirement in the Netherlands were Descartes’s productive period.  His motive in developing and writing out his thoughts was, essentially, the desire not to disappoint the widely spread belief that he was in possession of a philosophy more certain than the common one.  The work entitled Le Monde, begun in 1630 and almost completed, remained unprinted, as the condemnation of Galileo (1632) frightened our philosopher from publication; fragments of it only, and a brief summary, appeared after the author’s death.  The chief works, the Discourse on Method, the Meditations on the First Philosophy, and the Principles of Philosophy appeared between 1637 and 1644,—­the Discours de la Methode in 1637, together with three dissertations (the “Dioptrics,” the “Meteors,” and the “Geometry"), under the common title, Essais Philosophiques.  To the (six) Meditationes de Prima Philosophia, published in 1641, and dedicated to the Paris Sorbonne, are appended the objections of various savants to whom the work had been communicated in manuscript, together with Descartes’s rejoinders.  He himself considered the criticisms of Arnauld, printed fourth in order, as the most important.  The Third Objections are from Hobbes, the Fifth from Gassendi, the First, which were also the first received, from the theologian Caterus of Antwerp, while the Second and Sixth, collected by Mersenne, are from various theologians and mathematicians.  In the second edition there were added, further, the Seventh Objections, by the Jesuit Bourdin, and the Replies of the author thereto.  The four books of the Principia Philosophiae, published in 1644 and dedicated to Elizabeth, Countess Palatine, give a systematic presentation of the new philosophy.  The Discourse on Method appeared, 1644, in a Latin translation, the Meditations and the Principles in French, in 1647.  The Treatise on the Passions was published in 1650; the Letters, 1657-67, in French, 1668, in Latin.  The Opera Postuma, 1701, beside the Compendium of Music (written in 1618) and other portions of his posthumous writings, contain the “Rules for the Direction of the Mind,” supposed to have been written in 1629, and the “Search for Truth by the Light of Nature.”  The complete works have been often published, both in Latin and in French.  The eleven volume edition of Cousin appeared in 1824-26.[1]

[Footnote 1:  Of the many treatises on the philosophy of Descartes those of C. Schaarschmidt (Descartes und Spinoza, 1850) and J.H.  Loewe, 1855, may be mentioned.  Further, M. Heinze has discussed Die Sittenlehre des Descartes, 1872; Ed. Grimm, Descartes’ Lehre von den angeborenen Ideen, 1873; G. Glogau, Darlegung und Kritik des Grundgedankens der Cartesianisch.  Metaphysik (Zeitschrift fuer Philosophie, vol. lxxiii. p. 209 seq.), 1878; Paul Natorp, Descartes’ Erkenntnisstheorie,