at Paris; of both which philosophical institutions he had the honour to be elected a member. These were successively followed by numerous papers on mathematical and physical subjects, most of which have been preserved in a literary journal, published at Leipsic, under the title of "Acta Eruditorum." (§ 262.) At the same time, this indefatigable and almost universal genius was employed in preparing, at the request of the Duke of Lunenburg, a "History of the House of Brunswick;" several works on "The Law of Nations;" and some metaphysical tracts on "Knowledge, Truth, Ideas, Nature," &c. &c.

392. Passing over that remarkable fact connected with the literary history of Leibnitz, which relates to the invention of the differential calculus, (the particulars of which have been already detailed, § 264–266,) we shall advance to that period of his life, in which he was chiefly occupied with metaphysical speculations and theological controversies.

In 1695, he published, in a Parisian journal, a specimen of a new system of physics, in which he first intimated those peculiar doctrines relative to the connexion between the body and mind, which were afterwards more fully developed, and characterize his metaphysical system. This was followed by a treatise, entitled "Thoughts on Locke's Essay on the Human Understanding," then recently published. In this tract Leibnitz first appears as the antagonist of our great philosopher, and combats especially those parts of his celebrated work, which relate to innate ideas. The next production of

his pen on metaphysical subjects, was a defence of his favourite doctrine of the pre-established harmony, in reply to the animadversions which Bayle and others had made upon it in literary journals. About the same period, his active mind was also employed in polemic theology; as is evident from two controversial tracts,-one, "A Logical Defence of the Holy Trinity," written against the Socinians; and the other, "on Human Liberty and Predestination," against the Remonstrants.

393. But his principal work, the production of his later years, and that in which his philosophical opinions were more fully developed, remains to be noticed. This was entitled, "Theodicea, or a Dissertation on the Goodness of God, the Liberty of Man, and the Origin of Good and Evil." This celebrated treatise was first printed in 1710, and made a great stir amongst the metaphysicians of that day. It evinced an immense store of erudition, a mind well disciplined to abstract logical reasoning, a lively imagination, and a highly cultivated taste; but at the same time, it discovered a love of novelty and fondness for speculation unworthy of a sound philosopher, and wholly at variance with the principles of inductive reasoning. By these metaphysical and polemic writings, he became involved in wearisome controversies with some of the most enlightened intellectual philosophers of that brilliant age; among whom were Locke and Newton, Clarke and Bayle, with many others of inferior name. The details of these intellectual combats, on subjects the most abstruse and difficult that perhaps have ever occupied

the human understanding, will be chiefly found in the volume of his works which contains his correspondence with learned men; and which, while they excite our admiration of the powers of genius exerted in their discussion, convince us that there are topics, about which the busy and inquisitive mind of man may sometimes be employed, in the investigation of which the mightiest intellects are but as little children. This indefatigable writer exhausted his latest energies in these abstruse speculations, and expired on the 14th November, 1716, in the seventieth year of his age.

SECTION XI.

SUMMARY VIEW OF THE PHILOSOPHY OF LEIBNITZ.

394. LEIBNITZ did not compose any systematic treatise on philosophy; but his opinions may be gathered from his numerous writings, composed at different periods of life. The volume, in which his metaphysical system is most distinctly stated, is his "Theodicea," to which a reference was made in the last section; from which, therefore, the following summary will be chiefly taken. It is of the more importance that the distinguishing features of the philosophy of Leibnitz be attentively marked, because of the influence it excited long after the death of its illustrious founder. While the metaphysics of Locke may be considered as laying the foundation of a new school of intellectual philosophy

in Britain, which has subsequently spread over a great part of the world, those of Leibnitz must also be acknowledged to have influenced, in no inconsiderable degree, the speculations and researches of most of the intellectual philosophers-Kant himself not excepted. To the opinions and writings of Leibnitz, in the judgment of Professor Stewart, is chiefly to be attributed the contrast between the continental philosophy, and the contemporary systems, which have sprung up in our own island.

395. On the nature of ideas, and the manner in which they are produced, there is no material difference between Leibnitz and his illustrious predecessor, Des Cartes, who had himself derived his notions on this subject from the Platonic school. (§ 191.)-Nor is it easy to mark a difference between the opinions of both Des Cartes and Leibnitz, and those of Locke, except in words: for Leibnitz, when writing on the origin of ideas, asserts, "that there is nothing in the understanding which has not been present to the senses, but the understanding itself; and Locke, in nearly similar terms, writes thus : "External objects furnish the mind with ideas of sensible qualities; and the mind furnishes the understanding with ideas of its own operations." This cannot therefore be considered as forming a distinctive feature of the philosophy of Leibnitz; and those which are properly such, may be classed under four heads-his theory respecting Monads; his doctrine of the Pre-established Harmony; his scheme of Optimism; and his application of the "Law of

Continuity" to the phænomena of mind as well as of matter.

I MONADS.

396. Having imbibed the Cartesian notion of a plenum, and conceiving that the entire universe is filled with indivisible and uncompounded particles, he was led thereby to the fanciful hypothesis, that all space is replenished with a kind of substances called monads; by which he seems to have meant elementary active principles of nature, each of which is necessarily distinct from and independent of every other in the universe; but all of which derived their existence from God, the Great Supreme; and only self-existent monad. After all that Leibnitz has written on the subject of these mysterious substances, and all the explanations of his theory attempted by subsequent commentators, it is scarcely possible to attach any definite idea to the term, if any thing is intended by it, but the ultimate particles, of which the material universe is composed; in which case, it will appear to be but a modification of the ancient atomic philosophy. Yet it should seem, that this theoretical philosopher conceived of these monads as something different both from matter and spirit. They are not material, because he denied to them the properties of extension, durability, inertness, and other essential properties of matter. They are not spiritual, because he neither considered them as animated or rational. So attached was Leibnitz to this favourite hypothesis, that it seems to have pervaded his whole