(First of a three-part series.. Primary references.)

On this day in 1676 (or thereabouts), the young Gottfried Leibniz secretly traveled to the Hague to meet with the esteemed and dangerous Baruch de Spinoza. The two met for at least three days, during which Leibniz pressed him on the points of their philosophies that had the most in common, which worried Leibniz greatly. To be a Spinozist was to be an atheist and a heretic, and to be an atheist and a heretic was a very bad thing for one’s reputation and career, such that denying that one’s philosophy amounts to Spinozism is something of a necessary hobby during the early modern period.

But before we discuss their secretive meeting, we should discuss the host. Leibniz may have been the smartest man ever, but Spinoza may have been the more rigorous and honest philosopher. Spinoza was born into the Jewish community in Amsterdam in 1632. The Jewish community, recent exiles from Spain and Portugal, enjoyed relative religious freedom in Amsterdam, on one condition: that they conduct themselves according to the orthodoxy of their own religious tradition, in order to keep them from weighing in on the various Christian theological controversies (and resulting political struggles) in the city.

The community enforced intellectual order by banning or excommunicating heretics, insulating themselves from reprisal by removing the offending thoughts and the offender from the community. It was relatively common for the offender to be able to regain standing in the community by atoning.

Not so in the case of young Baruch. At age 24, on July 27, 1656, he was excommunicated with a proclamation that is notable for its vitriol and for the sheer joy one can induce in one’s undergraduates by reading it aloud in class:

…By decree of the angels and by the command of the holy men, we excommunicate, expel, curse, and damn Baruch de Espinoza, with the consent of God, Blessed be He, and with the consent of the entire holy congregation…

Cursed be he by day and cursed be he by night; cursed be he when he lies down and cursed be he when he rises up. Cursed be he when he goes out and cursed be he when he comes in. The Lord will not spare him, but the anger of the Lord and his jealousy shall smoke against that man, and all the curses that are written in this book shall lie upon him, and the Lord shall blot out his name from under heaven…

… No one should communicate with him, neither in writing, nor accord him any favor, nor stay with him under the same roof, nor come within four cubits of his vicinity; nor shall he read any treatise composed or written by him.

For his part, Spinoza claimed to be relatively unperturbed, saying that his “…departure will be more innocent than was the exodus of the early Hebrews from Egypt.” After his excommunication, he published under the Latin equivalent of his first name, Benedictus.

What had angered them so? It seems to have been a combination of his studies at the heterodox school led by the freethinker van den Enden, and his developing heterodox views about the status of the Jewish community, the rejection of divine creation, the denial of both the freedom of will and the immortality of the soul. All stem from his budding naturalism.

Spinoza’s views can be sketched in one phrase: he went where Descartes should have gone. We can color in that sketch by describing his views as a consequence of his naturalism, a commitment to the idea that:

1. Everything plays by the same rules.
2. The rule according to which everything plays is the principle of sufficient reason.

The second idea explains the first. The principle of sufficient reason (PSR) is the idea, roughly, that there are no brute facts, that the answer to ‘why?’ is never simply ‘because’, that everything at bottom is intelligible. Thus the first rule, because a distinction between the natural and the supernatural would be a brute fact, and brute facts are ruled out by his commitment to the PSR.

So, a recipe for Spinozism: take a rough approximation of the Cartesian concepts, add to them the PSR, and unlike Descartes, do not draw up lame when confronted with the possibility of contradicting orthodoxy. Spinoza’s geometrical method is seductive. Reading the Ethics (which was published posthumously), one at first finds oneself in familiar sunny Cartesian territory in the definitions and axioms: substance, attribute, mode, indivisibility, infinity, God, the PSR. Nothing seems scary or heterodox; it’s a pleasant stroll down familiar Aristotelian garden-paths. This surely leads us to a happy place full of pineal glands and mind-body duality, the goodness of God and the immortality of the soul.

And then, a shadow across the sun; by 1p5 (that is, proposition 5 of book 1) one can see where this is going; by 1p11, one should start to sweat; and by 1p14, Spinoza has proven substance monism, that the only truly independent thing is “God, or Nature” on Descartes’ own ground. Shortly thereafter, the denial of the freedom of the will, unactualized possibilities and the immortality of the soul follow.

Masterful. And, as we shall see, terrifying to the young Leibniz.