Prophetic Brains in a Vat


My latest blog post for The Jerusalem Post:

“Brains in a vat”?

It sounds like the plot of a bad science fiction movie. But it might hold a key to understanding prophetic insight.

The basic idea was around even before the writing of the Torah. In fact, Moses’ encounter with God on Sinai incorporates it: The idea that there are, or might be, aspects of reality that transcend our ability to perceive or understand.

On Sinai, Moses cannot see God’s face, only His back; and the rest of the Israelites cannot even see that.1 Across the Mediterranean, in ancient Athens, Plato wrote about people who had lived their entire lives chained in a cave, and knew the outside world only by the shadows it cast upon the cave wall.2 In Medieval Egypt, the Jewish sage Saadia Gaon realized that our minds were unable to comprehend the infinite.3

The late Hilary Putnam, author of Jewish Philosophy as a Guide to Life, explained it this way in modern terms:

“Imagine that a human being has been subjected to an operation by an evil scientist. The person’s brain has been removed from the body and placed in a vat of nutrients which keeps the brain alive. The nerve endings have been connected to a super-scientific computer which causes the person whose brain it is to have the illusion that everything is perfectly normal. There seem to be people, objects, the sky, etc., but really all the person is experiencing is the result of electronic impulses travelling from the computer to the nerve endings.”4

What if we are all brains in a vat?

Putnam takes it a step further: Suppose that we are all just brains in a vat, and moreover, that we have always been in the vat. When we perceive and refer to “solid objects” around us, all we are really perceiving are the illusions created by the computer.

Could we know that we were not walking around, perceiving things, and doing things? That we didn’t even have physical bodies, and were instead just brains in a vat? Putnam says no:

“The supposition that we are actually brains in a vat, although it violates no physical law and is perfectly consistent with everything we have experienced, cannot possibly be true. It cannot possibly be true because it is, in a certain way, self-refuting.”5

There are three problems with it.

First, all the things we know about — trees, cars, our bodies, and so forth — are illusions created by the computer. The words we use refer only to those illusions. As a result, when we talk about those things, we are not actually mistaken. We think they are “real,” and in the only sense that the word “real” has meaning for us, they are real. The illusions are all we know. We just don’t know that they are illusions. If we talk about trees, for example:

“There is no connection between the word ‘tree’ as used by these brains and actual trees. They would still use the word ‘tree’ just as they do, have just the images they have, even if there were no actual trees.”6

Second, if the computer program works correctly, the illusory world of the vat contains no strong evidence that anything else exists outside it.

Third, because all of our ideas and language refer only to our illusory world, we lack even the concepts to think about anything outside it. Our meaning for “outside” is based on our perception of spatial relationships in the illusory world of the vat. It only has meaning for us in that context. The outside world might exist, but we couldn’t know or understand anything about it. We lack both the evidence and the required concepts.

Prophetic insight thinks outside the vat

So how does that help explain prophetic insight?

Let’s add one element to Putnam’s scenario. Suppose there is an electric generator outside the vat. It powers the computer, but it also creates a weak magnetic field that extends into the vat.

A few of the brains are particularly sensitive, and the magnetic field causes some of their neurons to fire. As a result, they have strange experiences that they can’t explain in terms of the vat’s language and conceptual scheme. They resort to images, poetry, and metaphor to express what they’ve experienced. It’s a version of prophetic insight.

Of course, that story doesn’t prove anything. It’s just an analogy. But it shows how prophetic insight might work, and why prophetic visions often can’t be expressed in ordinary terms. In the nature of the case, it can’t be proven or disproven by science. You either believe it or you don’t.

A scientific analogy

There is, however, a similar scientific example. In 1964, physicists Arno Penzias and Robert Wilson at Bell Labs were trying to eliminate radio interference with communications satellites. They discovered a faint cosmic background radiation that is now believed to be a remnant of the “big bang” – a huge explosion about 13.8 billion years ago that created the physical universe.7

The cosmic background radiation is a faint echo of the universe’s beginning. We can’t normally detect it, but if we point the right instruments in the right direction, we can.

What about our own built-in instrument: our minds? We can’t normally detect a reality that transcends our universe. But if we point our minds in the right direction, and through prayer, meditation, or other means tune to just the right spiritual frequency, can we hear the voice of God? Is that what Moses and other ancient prophets did?

Maybe. It’s worth thinking about. Even if you have to “think outside the vat.”

Works Cited

Cornford, F., translator (1945), The Republic of Plato. Oxford: Oxford University Press.

Greene, B. (2003), The Elegant Universe. New York: W.W. Norton & Company. Kindle edition.

Putnam, H. (1981), Reason, Truth, and History. Cambridge: Cambridge University Press. Kindle edition.

Putnam, H. (2008), Jewish Philosophy as a Guide to Life. Bloomington: Indiana University Press.

Rosenblatt, S., translator (1948), Saadia Gaon: The Book of Beliefs and Opinions. New Haven: Yale University Press.


  1. Exodus 33:18-22. 
  2. Cornford, F. (1945), p. 227ff (Chapter 25 of The Republic). 
  3. Rosenblatt, S. (1948), pp. 98ff (Treatise II: “Concerning the Belief That the Creator of All Things, Blessed and Exalted Be He, Is One”). 
  4. Putnam, H. (1981), loc. 180. 
  5. Ibid, loc. 190. 
  6. Ibid, loc. 282. 
  7. Greene, B. (2003), loc. 5546. 

About N.S. Palmer

N.S. Palmer is an American mathematician.
This entry was posted in Epistemology, Jewish Philosophy, Judaism, Philosophy, The Jerusalem Post and tagged , , , , , , , , , , . Bookmark the permalink.

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