Here presents itself the ancient insoluble enigma. How can bodies act upon each other ? How can matter be moulded or modified by vital action? How can it be subdued or directed by the inteUigent volition of man ? How can it be conjoined with spirit in any form of animate existence ? Des Cartes so completely con- tradistinguished mind and matter that it was impossi- ble for mind to act upon matter or matter upon mind — frustrnferro dicerberat uinbms. Leibnitz so complete- ly assimilated material to spiritual existence, giving body to spirit, and spirit to body {Theod. § 124), that they were indistinguishable except by their properties —the one possessing perception only, the other having apperception also. There could be no intercommunion, no reciprocal influence between them, or between any monads. ^ To cut rather than to loose the intellectual knot, which was only rendered more intricate, Leibnitz proposed an explanation in his Systema Naturm (1(395). It is his celebrated doctrine oi Pre-established Harmomj. The monatls are forces, sometimes active, sometimes suspended, tvipyeini and SvvdjUK;, governed by their ovm inherent tendencies, and without i)ower of acting upon each other; but their separate actions are so fore- known on one side, and predetermined (in the. other, in the moment of creation, that their concurrent evolutions reciprocally correspond, and effectuate all the phenom- ena of the universe. ]\Iind, therefore, does not coerce matter, nor does one form of matter control another, but the inclination of the will and the disposition of the
matter, or the diverse evolutions of different monads, conjoin independently and without connection in the production of one result, in consequence of the pread- aptation of all the elementary forces to that particular change, at that particular moment, in that particular composition, and with that particular consequence. Du- gald Stewart illustrates this harmony by the supposi- tion of two clocks so regulated and adjusted as to strike the hours in unison. It may be an illustration; it is scarcely an elucidation of the doctrine. The agreement is only in time and performance : there is no concord- ance of dissimilar processes. The machinery of Divine A ssistance, which Des Cartes had employed for the ex- planation of the phenomena of animal life, was general- ized by Leibnitz, applied to the whole order of things, and transferred to the original of all creation. There is thus much more than a poetic symbolism — there is a tUstinctive philosoi:)hical tenet involved in his fine ex- pression that " the iniiverse is the knowledge of God." This preordination of concurrences, apt for each occa- sion, between monadic developments, each of which is determined by its own inherent force, which is will in intelligences and nature in material things, makes the whole endless series of change the reahzation of fore- seen and prearranged correspondences. It is the con- tinual evolution of the immeasurable plan entertained by the Creator before the beginning of the ages, and brought into act at the appointed time and in the ap- pointed order, with mathematical precision, though be- yond the calculation of mathematical devices. Certain fabrics are curiously woven with colors so arranged in the yarn that when the weaving is performed each col- or falls with exact propriety into its due place, and con- tributes accurately to form, to tint, to perfect the con- templated pattern. So, in the system of pre-established harmony, " the web of creation is woven in the loom of time," with threads prepared from the beginning to fall into the requisite connections, and to produce a fore- known design. Each concurrent movement arrives at the appropriate time and place in consequence of the whole antecedent series of changes in each case, for no- \vhere is there any solution of continuity, and the pres- ent is alwaj's the jirogeny of the past and the parent of the future. The innumerable lines of evolution contin- ually interosculate with each other, but never are blend- ed together. It wiU readily be perceived that the whole intricate phantasmagoria of these unconnected monads is only a grand and beautiful variation of the Cartesian hypothesis, and is neither more valid nor more satisfac- tory than the fantasy it was designed to supplant.
This doctrine of pre-established harmony is in per- fect consonance with Leibnitz's vindication of the ways of God to man, if it did not necessitate his theological expositions. The Tkeodicee is the most exquisite, the most brilliant, the most profound, the most learned, and, in some respects, the most satisfactory of all treatises of philosophical theology. Many of its conclusions are either true, or as near the truth as the human intellect can attain in such inquiries. Others are merely con- jectural, and are sometimes fantastic, as they lie beyond the domain of possible knowledge. Several of its posi- tions have furnished pretexts for sweeping censures; but in such speculations error is inevitable, and a slight error opens the way for a host of pernicious and unde- signed heresies. The most notable and characteristic of Leibnitz's theological dogmas, which provoked the malicious wit of Voltaire's Candide, is intimately asso- ciated with the explanation of the combined action of monads. This is the theory known as Optimism. With- out absolutely asserting that "Whatever is. is best," it alleges that the actual world is the best of all possible worlds, despite of acknowledged evils and defects. This is suppose(l to be "proved, among other evidences, by the Leibnitzian principle of the sufficient reason, suice, if any better world had been possible, it is reasonable to suppose that it would have been selected by God in preference to that which He actually created. The acute