One substance, and what follows from it
Why Spinoza Is the Philosopher Every Scientist Should Read
Spinoza is hard work at first — dense, geometrical, uncompromising. He wrote his Ethics like Euclid: definitions, axioms, proofs, as if metaphysics could be done with the rigour of geometry. Most readers give up quickly. I think scientists in particular are missing the most by it.
He started where a scientist would: with causation. Everything is the effect of some cause; to understand a thing just is to understand why it is as it is. Apply that to the idea of substance — something that exists in its own right — and a startling conclusion follows. A real substance must be the cause of itself; if it depended on anything outside, it would not be fundamental. But only one thing has no outside: the universe as a whole. Spinoza called it Deus sive Natura — God, or Nature. God and the universe are one.
This is nearly the opposite of theology. Spinoza’s God is not a person, a designer, or an agent who intervenes. It is the rational order of everything that exists, taken whole — lawful, self-contained, the same for every observer. Strip “God” of its anthropomorphism and what is left is something a physicist can use: a single, self-grounded reality whose behaviour follows from its own nature.
Two consequences should interest a scientist.
The mind–matter problem dissolves. Descartes left mind and matter as two substances interacting across a gap nobody could explain; Spinoza denies there are two. They are attributes of one substance — parallel expressions of the same reality, like the colour and the smell of a sausage on the grill, changing together. No interaction, because nothing is separate.
And there is the question of necessity. Spinoza’s own answer is uncompromising: everything follows from the nature of the whole, so nothing could have been otherwise. Freedom, on his account, is not exemption from that; it is acting from your own nature rather than being pushed by outside causes. A hard saying — and the same world the sciences assume when they look for laws rather than miracles. This is the one place I do not follow him all the way: on my account necessity belongs to the structure, and what actually fills it is contingent. But the disagreement is inside his framework, not against it.
I find no flaw in his reasoning, and I have looked, because my own framework rests on it.
To reject his conclusion you have to find the broken step, not just dislike where it lands. I have not found it. Much of my work develops his position with four centuries of science he did not have — reaching the same summit by a different route, through dimension, mind, and the observer. Two paths to one place is not proof; I call it encouragement. But it is not nothing.
You need not accept any of that to gain from him. Read Spinoza for the method, for the one-substance solution to a problem still open, and because he sketched — three and a half centuries early — a universe physics keeps making more plausible, not less.
Where to go next
Both are free, and both are running now. The essays come out twice a week; the video course builds the argument from the beginning, a new one every few days.
A longer version of this essay is on Substack. Where this account has changed, or where I have been wrong, it is on the corrections page.