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Leibniz, Kant, and the Possibility of Metaphysics (and Some Ado About Nothing)
By Brandon C. Look
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While all previous philosophers were, in (above) Immanuel Kant’s mind, guilty of various errors, Gottfried Wilhelm Leibniz occupied a special position in his conception of the history of philosophy and the history of reason’s pretensions. |
If the eighteenth century is to be seen as the “Age of Reason,” then one of the crucial stories to be told is of the trajectory of philosophy from one of the most ardent proponents of the powers of human reason, Gottfried Wilhelm Leibniz (1646–1716), to the philosopher who subjected the claims of reason to their most serious critique, Immanuel Kant (1724–1804). Not only is the story of Kant’s Auseinandersetzung with Leibniz important historically, it is also important philosophically, for it has implications about the nature and possibility of metaphysics, that branch of philosophy concerned with fundamental questions such as what there is, why there is anything at all, how existing things are causally connected, and how the mind latches onto the world. Like many philosophical debates, however, it is also prone to a kind of “eternal recurrence” to those who are ignorant of it.
Leibniz was a “rationalist” philosopher; that is, he was committed to two theses: (i) he believed that the mind has certain innate ideas—it is not, as John Locke and his fellow empiricists say, a tabula rasa or blank slate; and (ii) he believed in—and, in fact, made explicit—the “principle of sufficient reason,” according to which “there is nothing for which there is not a reason why it is so and not otherwise.” This principle had enormous metaphysical consequences for Leibniz, for it allowed him to argue that the world, as a series of contingent things, could not have the reason for its existence within it; rather there must be an extramundane reason—God. Further, as a response to the mind-body problem, Leibniz advanced the theory of “pre-established harmony,” according to which there is no interaction at all between substances; the mind proceeds and “unfolds” according to its own laws, and the body moves according to its own laws, but they do so in perfect harmony, as is fitting for something designed and created by God. Strictly speaking, however, Leibniz was not a dualist; he did not believe that there were minds and bodies—at least not in the same sense and at the most fundamental level of reality. Rather, in his mature metaphysical view, there are only simple substances, or monads, mind-like beings endowed with forces that ground all phenomena. Finally, according to Leibniz, since these simple substances are ontologically primary and ground the phenomena of matter and motion, space and time are merely the ordered relations derivative of the corporeal phenomena. Leibniz contrasted his view with that of Isaac Newton, according to whom there is a sense in which space and time can be considered absolute and space can be considered something substantial.
Is the Solar System Stable?
By Scott Tremaine
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Scott Tremaine explores the stability of our solar system, one of the oldest problems in theoretical physics, dating back to Isaac Newton. |
The stability of the solar system is one of the oldest problems in theoretical physics, dating back to Isaac Newton. After Newton discovered his famous laws of motion and gravity, he used these to determine the motion of a single planet around the Sun and showed that the planet followed an ellipse with the Sun at one focus. However, the actual solar system contains eight planets, six of which were known to Newton, and each planet exerts small, periodically varying, gravitational forces on all the others.
The puzzle posed by Newton is whether the net effect of these periodic forces on the planetary orbits averages to zero over long times, so that the planets continue to follow orbits similar to the ones they have today, or whether these small mutual interactions gradually degrade the regular arrangement of the orbits in the solar system, leading eventual ly to a collision between two planets, the ejection of a planet to interstellar space, or perhaps the incineration of a planet by the Sun. The interplanetary gravitational interactions are very small—the force on Earth from Jupiter, the largest planet, is only about ten parts per million of the force from the Sun—but the time available for their effects to accumulate is even longer: over four billion years since the solar system was formed, and almost eight billion years until the death of the Sun.
