Jakob Thomasius

Jakob Thomasius: The Heresy-Hunter Who Founded a Discipline

In 1661 a fourteen-year-old arrived at the University of Leipzig and fell under the supervision of the professor of rhetoric and moral philosophy. The boy was Gottfried Wilhelm Leibniz, and the professor, Jakob Thomasius, became his mentor, his adviser, and — for the rest of Thomasius's life — his correspondent. Leibniz would later describe him as "the most celebrated German Peripatetic." Thomasius had already taught Leibniz's father. He would end up teaching the seventeenth century how to write the history of philosophy, largely by trying to prove that most of it was heresy.

A Life Inside One City

Thomasius was born in Leipzig on 27 August 1622 and died in Leipzig on 9 September 1684, and in between he barely left. He took his B.A. at the university there in 1642 and his M.A. in 1643, studying under Friedrich Leibniz — father of the more famous Leibniz, which makes Thomasius a link in one of the tidier chains in intellectual history.

He held the chair of rhetoric, dialectic, and moral philosophy at Leipzig, and from 1670 to 1676 also served as rector of the Old St Nicholas School in the same city. Otto Mencke was among his doctoral students. It is the career of a working academic — no court appointment, no exile, no scandal — and the output is correspondingly enormous and correspondingly local.

The Correspondence with Leibniz

The most consequential thing Thomasius ever received was a letter. In April 1669 Leibniz wrote to his old teacher proposing that Aristotelian philosophy and the new mechanical philosophy could be reconciled — that the moderns had not refuted the Schoolmen so much as re-described them. Leibniz published it in 1670 under a title addressed to a man of the most refined learning, and it stands as his first public presentation of the theory of substance that would occupy him for the next fifty years.

That the letter was written to Thomasius is not incidental. Thomasius was the conciliator in German philosophy, the man who held that Aristotle and Christian doctrine fitted together and that the moderns had not made scholasticism obsolete. Leibniz was writing to the person whose entire position his proposal was designed to vindicate. The seed of one of the great metaphysical systems of Europe was planted in a letter to a Leipzig rhetoric professor.

Schediasma Historicum

Thomasius's decisive book appeared in 1665. The *Schediasma historicum* was, on its face, a work of polemic: a radical and systematic attempt to separate pagan philosophy from biblical religion, to draw a hard line and put Plato on the wrong side of it.

Its method, however, was historical. To show that pagan philosophy was incompatible with Christianity, Thomasius had to trace pagan doctrines through their sources, establish who took what from whom, and follow ideas across centuries as ideas — a genealogy of error. That procedure, undertaken for hostile reasons, is recognisably the procedure of the history of philosophy as a scholarly field. He is regarded as an important founding figure in the scholarly study of the history of philosophy, and Wouter Hanegraaff has argued that the *Schediasma* gave birth to the first actual study of Western esotericism. Thomasius built the discipline while building the case for the prosecution.

The Two Errors

His charge sheet was precise. Two pagan assumptions, he held, could never be reconciled with Christianity: that the world was coeternal with God, and that human beings could attain knowledge of their own divine nature through *gnosis*. Both violate the point on which Thomasius was immovable — the absolute separation of Creator and Creation. Philosophy, on his account, should proceed from Christian Aristotelianism, and Stoicism and Neoplatonism were not alternative options but contaminations. His *Dissertationes ad stoicae philosophiae* of 1682 pursued the Stoics on the same grounds.

He also made a prediction, and it was a good one. New forms of Platonic spiritualism, he wrote, would keep arising as long as individuals embraced the Platonic doctrines of emanation and self-salvation. The history of the following three centuries of Western esotericism is, from a certain angle, a long confirmation.

The First Shot at Spinoza

In the same combative spirit, Thomasius produced what is credited as the earliest published critique of Spinoza's *Theological-Political Treatise* — the first man in Europe into print against the book that would define the century's argument about God, nature and the state. The charge he pressed was naturalism and its political dangers, which is to say the same charge as always: a philosophy that collapses the distance between Creator and Creation. Whatever one makes of the argument, the reflex is characteristic. He read the most alarming new work available and answered it in public before anyone else had.

His interests were not confined to combat. He wrote on plagiarism, and in 1671 published *De foeminarum eruditione* — on the learning of women — a subject a Leipzig moral philosopher of the 1670s was under no obligation whatever to take up.

Why Jakob Is Called a Genius

The claim rests on a peculiar and rare kind of intellectual achievement: inventing a method that outlives the purpose it was invented for. Thomasius wanted to condemn pagan philosophy. To condemn it accurately he had to reconstruct it accurately — sources, transmission, dependencies, the drift of a doctrine from Plotinus down through the centuries. Nobody had done this systematically. In doing it, he produced the template for the history of philosophy as a discipline, and, on Hanegraaff's reading, the founding document of the academic study of Western esotericism. The prediction about recurring Platonic spiritualism shows the same faculty: an ability to see a body of ideas as a structure with a trajectory rather than as a heap of opinions. His judgement of talent was equally sharp — he took a fourteen-year-old seriously, and that fourteen-year-old sent him the first draft of the theory of monads.

The counter-case is real and should not be softened. Thomasius originated no philosophical position of his own. His substantive commitment was Christian Aristotelianism, a conservative holding action, and the *Schediasma* is at bottom a heresiography — scholarship in the service of a foregone conclusion, which is a poor recipe for accuracy. Hanegraaff's own use of him is as the origin of a long disparagement, a framework later carried on by Heumann and Brucker, that shut a whole tradition out of serious study for two centuries. Modern reference works name Brucker, not Thomasius, as the father of philosophical historiography. Thomasius was eclectic, industrious, and formidably learned; whether the man who accidentally invented a field while poisoning its subject matter deserves the word "genius" depends on how much credit accident earns.

Legacy

His methods passed to his son. Christian Thomasius (1655–1728) took up his father's eclectic approach and became a philosopher and jurist of considerably greater fame than the man who trained him. The father supplied the tools; the son found wider use for them.

Leibniz kept writing to him until he died. It is a decent measure of a teacher that the most powerful mind of the age never stopped reporting back.

Achievements

• Held posts at Leipzig University
• Fields: philosopher