4. The last word of materialism was spoken with reckless audacity by _La Mettrie_ (1709-1751), a contemporary of Diderot: every thing spiritual is a delusion, and physical enjoyment is the highest end of men. Faith in the existence of a God, says La Mettrie, is just as groundless as it is fruitless. The world will not be happy till atheism becomes universally established. Then alone will there be no more religious strife, then alone will theologians, the most odious of combatants, disappear, and nature, poisoned at present by their influence, will come again to its rights. In reference to the human soul, there can be no philosophy but materialism. All the observation and experience of the greatest philosophers and physicians declare this. Soul is nothing but a mere name, which has a rational signification only when we understand by it that part of our body which thinks. This is the brain, which has its muscles of thought, just as the limbs have their muscles of motion. That which gives man his advantage over the brutes is, first, the organization of his brain, and second, its capacity for receiving instruction. Otherwise, is man a brute like the beasts around him, though in many respects surpassed by these. Immortality is an absurdity. The soul perishes with the body of which it forms a part. With death every thing is over, _la farce est jouée_! The practical and selfish application of all this is—let us enjoy ourselves as long as we exist, and not throw away any satisfaction we can attain. 5. The _Systéme de la Nature_ afterwards attempted to elaborate with greater earnestness and scientific precision, that which had been uttered so superficially and so superciliously by La Mettrie, viz., the doctrine that matter alone exists, while mind is nothing other than matter refined. The _Systéme de la Nature_ appeared in London under a fictitious name in 1770. It was then published as a posthumous work of Mirabaud, late secretary of the Academy. It doubtless had its origin in the circle which was wont to assemble with Baron Holbach, and of which Diderot, Grimm, and others formed a part. Whether the Baron Holbach himself, or his tutor Lagrange is the author of this work, or whether it is the joint production of a number, cannot now be determined. The _Systéme de la Nature_ is hardly a French book: the style is too heavy and tedious. There is, in fact, nothing but matter and motion, says this work. Both are inseparably connected. If matter is at rest, it is only because hindered in motion, for in its essence it is not a dead mass. Motion is twofold, attraction and repulsion. The different motions which we see are the product of these two, and through these different motions arise the different connections and the whole manifoldness of things. The laws which direct in all this are eternal and unchangeable.—The most weighty consequences of such a doctrine are: