The question concerning the substantiality of mind and matter in relation to God, is involved from the very beginning in this latter problem, "How is the appearance of interaction between the two to be explained without detriment to their substantiality in relation to each other?" The denial of the reciprocal dependence of matter and spirit leads to sharper accentuation of their common dependence upon God. Thus occasionalism forms the transition to the pantheism of Spinoza, Geulincx emphasizing the non-substantiality of spirits, and Malebranche the non-substantiality of bodies, while Spinoza combines and intensifies both. And yet history was not obliging enough to carry out this convenient and agreeable scheme of development with chronological accuracy, for she had Spinoza complete his pantheism before Malebranche had prepared the way. The relation which was noted in the case of Bruno and Campanella is here repeated: the earlier thinker assumes the more advanced position, while the later one seems backward in comparison; and that which, viewed from the standpoint of the question itself, may be considered a transition link, is historically to be taken as a reaction against the excessive prosecution of a line of thought which, up to a certain point, had been followed by the one who now shrinks back from its extreme consequences. The course of philosophy takes first a theological direction in the earlier occasionalists, then a metaphysical (naturalistic) trend in Spinoza, to renew finally, in Malebranche, the first of these movements in opposition to the second. The Cartesian school, as a whole, however, exhibits a tendency toward mysticism, which was concealed to a greater or less extent by the rationalistic need for clear concepts, but never entirely suppressed.
Although the real interaction of body and mind be denied, some explanation must, at least, be given for the appearance of interaction, i.e. for the actual correspondence of bodily and mental phenomena. Occasionalism denotes the theory of occasional causes. It is not the body that gives rise to perception, nor the mind that causes the motion of the limbs which it has determined upon—neither the one nor the other can receive influence from its fellow or exercise influence upon it; but it is God who, "on the occasion" of the physical motion (of the air and nerves); produces the sensation (of sound), and, "at the instance" of the determination of the will, produces the movement of the arms. The systematic development and marked influence of this theory, which had already been more or less clearly announced by the Cartesians Cordemoy and De la Forge,[1] was due to the talented Arnold Geulincx (1624–69), who was born at Antwerp, taught in Lyons (1646–58) and Leyden, and became a convert to Calvinism. It ultimately gained over the majority of the numerous adherents of the Cartesian philosophy in the Dutch universities—Renery (died 1639) and Regius (van Roy; Fundamenta Physicae, 1646; Philosophia Naturalis, 1661) in Utrecht; further, Balthasar Bekker (1634–98; The World Bewitched, 1690), the brave opponent of the belief in angels and devils, of magic, and of prosecution for witchcraft—in the clerical orders in France and, finally, in Germany.
[Footnote 1: Gerauld de Cordemoy, a Parisian advocate (died 1684, Dissertations Philosophiques, 1666), communicated his occasionalistic views orally to his friends as early as 1658 (cf. L. Stein in the Archiv für Geschichte der Philosophie, vol. i., 1888, p. 56). Louis de la Forge, a physician of Saumur, Tractatus de Mente Humana, 1666, previously published in French; cf. Seyfarth, Gotha, 1887. But the logician, Johann Clauberg, professor in Duisburg (1622–65; Opera, edited by Schalbruch, 1691), is, according to the investigations of Herm. Müller (J. Clauberg und seine Stellung im Cartesianismus, Jena, 1891), to be stricken from the list of thinkers who prepared the way for occasionalism, since in his discussion of the anthropological problem (corporis et animae conjunctio) he merely develops the Cartesian position, and does not go beyond it. He employs the expression occasio, it is true, but not in the sense of the occasionalists. According to Clauberg the bodily phenomenon becomes the stimulus or "occasion" (not for God, but) for the soul to produce from itself the corresponding mental phenomenon.]
Geulincx himself, besides two inaugural addresses at Leyden (as Lector in 1662, Professor Extraordinary in 1665), published the following treatises: Quaestiones Quodlibeticae (in the second edition, 1665, entitled Saturnalia) with an important introductory discourse; Logica Fundamentis Suis Restituta, 1662; Methodus Inveniendi Argumenta (new edition by Bontekoe, 1675); and the first part of his Ethics—De Virtute et Primis ejus Proprietatibus, quae vulgo Virtutes Cardinales Vocantur, Tractatus Ethicus Primus, 1665. This chief work was issued complete in all six parts with the title, [Greek: Gnothi seauton] sive Ethica, 1675, by Bontekoe, under the pseudonym Philaretus. The Physics, 1688, the Metaphysics, 1691, and the Annotata Majora in Cartesii Principia Philosophiae, 1691, were also posthumous publications, from the notes of his pupils. In view of the rarity of these volumes, and the importance of the philosopher, it is welcome news that J.P.N. Land has undertaken an edition of the collected works, in three volumes, of which the first two have already appeared.[1] The Hague, 1891–92.[2]
[Footnote 1: On vol. i. cf. Eucken, Philosophische Monatshefte, vol. xxviii., 1892, p,200 seq.]
[Footnote 2: On Geulincx see V. van der Haeghen, Geulincx, Étude sur sa Vie, sa Philosophie, et ses Ouvrages, Ghent, 1886, including a complete bibliography; and Land in vol. iv. of the Archiv für Geschichte der Philosophie, 1890. [English translation, Mind, vol. xvi. p. 223 seq.]]
Geulincx bases the occasionalistic position on the principle, quod nescis, quomodo fiat, id non facis. Unless I know how an event happens, I am not its cause. Since I have no consciousness how my decision to speak or to walk is followed by the movement of my tongue or limbs, I am not the one who effects these. Since I am just as ignorant how the sensation in my mind comes to pass as a sequel to the motion in the sense-organ; since, further, the body as an unconscious and non-rational being can effect nothing, it is neither I nor the body that causes the sensation. Both the bodily movement and the sense-impression are, rather, the effects of a higher power, of the infinite spirit. The act of my will and the sense-stimulus are only causae occasionales for the divine will, in an incomprehensible way, to effect, in the one case, the execution of the movement of the limbs resolved upon, and, in the other, the origin of the perception; they are (unsuitable) instruments, effective only in the hand of God; he brings it to pass that my will goes out beyond my soul, and that corporeal motion has results in it. The meaning of this doctrine is misapprehended when it is assumed—an assumption to which the Leibnitzian account of occasionalism may mislead one—that in it the continuity of events, alike in the material and the psychical world, is interrupted by frequent scattered interferences from without, and all becoming transformed into a series of disconnected miracles. An order of nature