Now when preparing to justify my system in face of the new difficulties of M. Bayle, I purposed at the same time to communicate to him the ideas which I had had for some time already, on the difficulties put forward by him in opposition to those who endeavour to reconcile reason with faith in regard to the existence of evil. Indeed, there are perhaps few persons who have toiled more than I in this matter. Hardly had I gained some tolerable understanding of Latin writings when I had an opportunity of turning over books in a library. I flitted from book to book, and since subjects for meditation pleased me as much as histories and fables, I was charmed by the work of Laurentius Valla against Boethius and by that of Luther against Erasmus, although I was well aware that they had need of some mitigation. I did not omit books of controversy, and amongst other writings of this nature the records of the Montbéliard Conversation, which had revived the dispute, appeared to me instructive. Nor did I neglect the teachings of our theologians: and the study of their opponents, far from disturbing me, served to strengthen me in the moderate opinions of the Churches of the Augsburg Confession. I had opportunity on my journeys to confer with some excellent men of different parties, for instance with Bishop Peter von Wallenburg, Suffragan of Mainz, with Herr Johann Ludwig Fabricius, premier theologian of Heidelberg, and finally with the celebrated M. Arnauld. To him I even tendered a Latin Dialogue of my own composition upon this subject, about the year 1673, wherein already I laid it down that God, having chosen the most perfect of all possible worlds, had been prompted by his wisdom to permit the evil which was bound up with it, but which still did not prevent this world from being, all things considered, the best that could be chosen. I have also since read many and various good authors on these subjects, and I have endeavoured to make progress in the knowledge that seems to me proper for banishing all that could have obscured the idea of supreme perfection which must be acknowledged in God. I have not neglected to examine the most rigorous authors, who have extended furthest the doctrine of the necessity of things, as for instance Hobbes and Spinoza, of whom the former advocated this absolute necessity not only in his Physical Elements and elsewhere, but also in a special book against Bishop Bramhall. And Spinoza insists more or less (like an ancient Peripatetic philosopher named Strato) that all has come from the first cause or from primitive Nature by a blind and geometrical necessity, with complete absence of capacity for choice, for goodness and for understanding in this first source of things.
I have found the means, so it seems to me, of demonstrating the contrary in a way that gives one a clear insight into the inward essence of the matter. For having made new discoveries on the nature of active force and the laws of motion, I have shown that they have no geometrical necessity, as Spinoza appears to have believed they had. Neither, as I have made plain, are they purely arbitrary, even though this be the opinion of M. Bayle and of some modern philosophers: but they are dependent upon the fitness of things as I have already pointed out above, or upon that which I call the 'principle of the best'. Moreover one recognizes therein, as in every other thing, the marks of the first substance, whose productions bear the stamp of a supreme wisdom and make the most perfect of harmonies. I have shown also that this harmony connects both the future with the past and the present with the absent. The first kind of connexion unites times, and the other places. This second connexion is displayed in the union of the soul with the body, and in general in the communication of true substances with one another and with material phenomena. But the first takes place in the preformation of organic bodies, or rather of all bodies, since there is organism everywhere, although all masses do not compose organic bodies. So a pond may very well be full of fish or of other organic bodies, although it is not itself an animal or organic body, but only a mass that contains them. Thus I had endeavoured to build upon such foundations, established in a conclusive manner, a complete body of the main articles of knowledge that reason pure and simple can impart to us, a body whereof all the parts were properly connected and capable of meeting the most important difficulties of the ancients and the moderns. I had also in consequence formed for myself a certain system concerning the freedom of man and the cooperation of God. This system appeared to me to be such as would in no wise offend reason and faith; and I desired to submit it to the scrutiny of M. Bayle, as well as of those who are in controversy with him. Now he has departed from us, and such a loss is no small one, a writer whose learning and acumen few have equalled. But since the subject is under consideration and men of talent are still occupied with it, while the public also follows it attentively, I take this to be a fitting moment for the publication of certain of my ideas.
It will perhaps be well to add the observation, before finishing this preface, that in denying the physical influence of the soul upon the body or of the body upon the soul, that is, an influence causing the one to disturb the laws of the other, I by no means deny the union of the one with the other which forms of them a suppositum; but this union is something metaphysical, which changes nothing in the phenomena. This is what I have already said in reply to the objection raised against me, in the Mémoires de Trévoux, by the Reverend Father de Tournemine, whose wit and learning are of no ordinary mould. And for this reason one may say also in a metaphysical sense that the soul acts upon the body and the body upon the soul. Moreover, it is true that the soul is the Entelechy or the active principle, whereas the corporeal alone or the mere material contains only the passive. Consequently the principle of action is in the soul, as I have explained more than once in the Leipzig Journal. More especially does this appear in my answer to the late Herr Sturm, philosopher and mathematician of Altorf, where I have even demonstrated that, if bodies contained only the passive, their different conditions would be indistinguishable. Also I take this opportunity to say that, having heard of some objections made by the gifted author of the book on Self-knowledge, in that same book, to my System of Pre-established Harmony, I sent a reply to Paris, showing that he has attributed to me opinions I am far from holding. On another matter recently I met with like treatment at the hands of an anonymous Doctor of the Sorbonne. And these misconceptions would have become plain to the reader at the outset if my own words, which were being taken in evidence,