Tuesday, January 16, 2007

Stewart on Spinoza and Leibniz

Matthew Stewart, The Courtier and the Heretic: Leibniz, Spinoza, and the Fate of God in the Modern World (Norton, 2006). This is a very well-researched intellectual history of two of the so-called Rationalist philosophers of the 17th century, and its success with the public ought to tell publishers a lot about the public appetite for this kind of material. It takes a real talent to popularize this highly abstract subject. This is not a hard-core philosophy book, like reading Stuart Hampshire on Spinoza or Bertrand Russell on Leibniz, but enthusiasts will still enjoy Mr. Stewart's argument that Spinoza was the catalytic philosophical influence on Leibniz, and the thorough review of what is known about these two colorfully contrasting characters. Stewart's repudiation of the old "Rationalist/Empiricist" picture of Early Modern philosophy is right on. He offers a very consistent interpretation of Spinoza that sees him as a full-blown modern physicalist; Chapter 10 merits a careful once or twice through, and is mostly persuasive, as on the impossibility of a personal God or personal immortality on Spinoza's view. My main disagreement with Stewart on Spinoza is that he tends to collapse the mental aspect of things into the physical aspect of things too much. A mental description of a thing is, according to this interpretation, a particular species of physical description. It seems to me that Spinoza is insisting that everything can be understood as having both mental descriptions and physical descriptions, in the context of his metaphysically monist claim that everything is God. I think it is reductive to interpret Spinoza as a physicalist. Another problem is that Stewart doesn't appreciate the importance of modal logic for metaphysics, then and now. Spinoza thought that everything that existed existed necessarily, necessity following from the perfection of God. The idea was that contingency and possibility were illusions of human finitude. The ancients had the same problem from Parmenides to Aristotle, and it wasn't until Frege developed a way to formalize modal operators in the 19th century that logic could truly be said to represent the real world of accidents, contingencies and probabilities. But Leibniz anticipated all of this: he saw that God could still be seen as making a willful (and thus moral) decision in the creation of the world if God chose among possible worlds. Stewart conveys this well, making it the more surprising that he doesn't see where Leibniz went beyond Spinoza on the problem of determinism. Quantifying over the objects in sets of possible worlds is the way that modern computers represent/handle modal operations. The metaphysical implications of possible-worlds modeling is one of the core arguments in the recent revival of metaphysics, for example in debates between David Lewis and Alvin Plantinga. The young Bertrand Russell uncovered the forgotten Leibniz sources and made his own name with the publication of his book The Philosophy of Leibniz in 1900, one of the great interpretive coups of modern philosophy. Stewart waves the whole discussion off thusly: "Russell and others who sought to place the study of logic at the foundation of philosophy claimed to see in Liebniz's metaphysics an astonishingly prescient and coherent application of fundamental principles of logic." This implies that Stewart is a partisan who doesn't like the idea of "the study of logic at the foundation of philosophy," and is antagonized by Russell. Stewart never even bothers to explain possible worlds modeling: the fine index has 24 citations of "modernity," not one of "modality." But I doubt that I'm the only reader who picked up a popular discussion of Spinoza and Leibniz precisely because these metaphysical ideas are currently in the air.

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