I have spent a lot of my life dealing with crazy people, including myself. “Crazy,” of course, has various definitions, though it’s not the topic of this blog post. My favorite definition was given by the American writer Ambrose Bierce (1842-1914):
"Mad, adj.: Affected with a high degree of intellectual independence; not conforming to standards of thought, speech and action derived by the conformants from study of themselves; at odds with the majority; in short, unusual." 
A definition that’s less funny but more in accord with common sense is that people are crazy if they have beliefs, emotions, or compulsions inconsistent with leading happy, productive, fulfilling lives; or more seriously, that cause them to harm themselves or others. It describes most of us at one time or another.
Regardless of definition, my experience with crazy people leads me to conclude that logic and evidence are secondary when it comes to holding beliefs. The main reason people hold beliefs is that the beliefs do something for them.
In many cases, the “something” matches our ordinary model of beliefs. You want to get to the grocery store, so you consult your memory, check the city map, and perhaps activate the GPS app on your cell phone. That evidence supports a belief that the store is in a particular location and that you can reach it by a particular route. Based on the evidence, you believe it. It seems that the ordinary account of belief is correct. Case closed. Right?
Wrong. Why does the belief matter to you? Do you cherish it because of its abstract truth? No. You never give a thought to its abstract truth. Do you care a whit how you arrived at the belief? No. How you got the belief doesn't matter except to increase your confidence that it is correct. The belief itself has value because it helps you get to the store. It does something for you.
The situation becomes clearer when you’re dealing with “crazy” beliefs that have no ordinary and obvious justification: A man believes he’s Napoleon. A woman believes she’s married to Brad Pitt. Brad Pitt believes he’s Napoleon, and he challenges the first man to a duel. That kind of thing.
Unless there’s a brain disorder, what you find in such cases is that the beliefs serve some purpose for the believers. It’s not getting to the store, of course; nor is it commanding the French army. It’s often connected with the need to feel loved, important, or accepted by a peer group. But it’s not based on evidence. The beliefs do something for them.
What does all that have to do with Spinoza?
Spinoza was a genius, to be sure, but he was also a human being with emotional needs. He devised a radically new interpretation of God that satisfied those needs.
Oh, yes, he also had lots of arguments to support his beliefs; but we all have lots of arguments. Highly intelligent people have the most extensive and sophisticated arguments, as Spinoza did. But the psychological needs, and the need to satisfy them, come first.
As an Enlightenment-era rationalist and an admirer of the French philosopher Rene Descartes, Spinoza needed to feel that the world was intelligible. To merit his attention, any kind of reality had to make sense to him. If he couldn’t understand it, then it was hard for him to believe in it.
And though Spinoza was willing to challenge Jewish belief, he was still a Jew down to his bones. He had grown to maturity in that intellectual and spiritual environment. Whether he liked it or not, the Jewish tradition was part of him and he was part of it. It was important to him. For him, it just had to make sense somehow. It had to. He couldn’t rest until he figured out how.
And that’s where he ran into problems. Jewish rationalists such as Saadia and Maimonides had redefined Jewish belief in terms that made philosophical sense but were religiously useless. As an article in The Boston Globe observed last week:
"Following philosophers like Maimonides, God had become an abstract, practically inconceivable entity, which made the idea of prayer and religious observance seem almost absurd." 
Spinoza couldn’t live with that. He needed a God he could understand. But the unexplained God of Judah Halevi was no more help to him than the unexplainable God of Saadia and Maimonides.
In his Treatise on the Emendation of the Intellect, Spinoza revealed his deepest motivation:
"After experience had taught me that all the things which regularly occur in ordinary life are empty and futile ... I resolved at last to try to find out if there was anything which would be the true good ... if there was something which, once found and acquired, would continuously give me the greatest joy for eternity ... I would be giving up certain evils for a certain good." 
In essence, Spinoza “got saved.” He despaired of things that were “empty and futile,” but he found in reason something that could give him “the greatest joy for eternity.” That is the language not of a secular philosopher but of a fervent religious believer.
For his psychological salvation, Spinoza needed a God that he could understand rationally. Because he needed it, he found a way to believe in it:
“God, or substance consisting of infinite attributes, each of which expresses eternal and infinite essence, necessarily exists.” 
It's philosopher-talk for saying that God is the universe. God is more than just the universe, to be sure, but the universe is the aspect of God we can see and comprehend. Everything that exists is included in God, so the more we learn about the natural universe, the more adequately we form an idea of God:
“Whatever is, is in God, and nothing can be or be conceived without God.” 
That’s a God in which Spinoza could believe without reservation: Deus sive natura, the vast extended system of the physical universe with its parallel mental system of ideas. We understand it only imperfectly, but we can understand it.
Thus, Spinoza’s idea of “God as the universe” was ultimately rooted in his emotional need to believe that the world was rational and comprehensible. He couldn’t live with religious mysteries, so he didn’t.
Bierce, A. (2014), The Devil’s Dictionary. Seattle: Amazon Digital Services.
Shirley, S. translator (2011), The Ethics by Baruch de Spinoza. Indianapolis: Hackett Publishing.
1. Bierce, A. (2014), p. 121.
2. Glinter, E., “A Mysterious Medieval Text, Decrypted.” *The Boston Globe*, June 26, 2016.
3. Shirley, S. (2011), p. 233.
4. Ibid, p. 36; Proposition I.11.
5. Ibid, p. 40; Proposition I.15.