Ploucquet, Gottfried (1716–1790)
Gottfried Ploucquet, the German philosopher and logician, studied philosophy and theology at Tübingen, experiencing both Wolffian and Pietist influences. After serving as a pastor, he was professor of logic and metaphysics at Tübingen from 1750 to 1782. He was elected to the Berlin Academy in 1748. Ploucquet was one of the few logicians between Gottfried Wilhelm Leibniz and George Boole to study a symbolic calculus. In metaphysics, despite his Wolffian training, he developed a quite personal position inspired by René Descartes and Nicolas Malebranche and aimed at revising Leibnizianism on a theological basis.
Ploucquet regarded the problems of theology, cosmology, and psychology as inextricably intertwined, with theology as the predominant discipline. There were some variations in Ploucquet's doctrines, but typically he held that a monad is a spiritual substance, and that even being is spiritual. Spiritual substances and material things can interact because God represents both and connects them. Human perceptions are an effect of God's "real vision." Spiritual and material things are both real because God represents them; material things are real in a further sense, as phaenomena substantiata, insofar as God represents them as real. This divine representation is the cause of the real existence of things; but we perceive only an appearance of this real existence. Ploucquet showed, by an examination of the logical difficulties of the concept of infinity, that space and time cannot exist outside of human representation.
Ploucquet's philosophy was basically a pronounced metaphysical subjectivism and phenomenalism. But in order to escape the consequent idealism of this position, Ploucquet reintroduced a variety of realism based on God. Ploucquet's was one of the most significant attempts before Immanuel Kant to develop a phenomenalism that asserted the real existence of things but denied (contrary to Leibnizian and Wolffian phenomenalism) that we can know such things on the basis of their appearances.
See also Descartes, René; Leibniz, Gottfried Wilhelm; Logic, History of: Precursors of Modern Logic; Malebranche, Nicolas; Phenomenalism; Wolff, Christian.
principal works by ploucquet
Primaria monadalogiae capita. Berlin, 1747.
Principia de substantiis et phaenomenis. Frankfurt and Leipzig, 1752.
Fundamenta philosophiae speculativae. Tübingen, 1759.
Institutiones philosophiae theoreticae. Stuttgart, 1772.
Sammlung der schriften, welche den logischen Calkul des Herrn Prof. Ploucquets betreffen, mit neuen Zusätzen. Edited by F. A. Böck. Tübingen, 1773.
Elementa philosophiae contemplativae. Stuttgart, 1778.
Commentationes philosophicae selectiores. Utrecht, 1781.
works on ploucquet
Aner, Karl. Gottfried Ploucquets Leben und Lehre. Bonn, 1909.
Bornstein, Paul. Gottfried Ploucquets Erkenntnistheorie und Metaphysik. Potsdam: Buchdr. von A.W. Hayn's Erben, 1898.
Giorgio Tonelli (1967)