Tag Archives: Brain in a Vat

Hilary Putnam’s Model-Theoretic Argument for “Internal Realism”: Three Arguments against Reference, Part 2

Posted on by under Perception, structural realism

The first post in this series examined Hilary Putnam’s famous argument that a “brain in a vat” (BIV) could not know that it was a BIV—or even think or wonder whether it was a BIV—because its words and thoughts would lack the causal-perceptual links to vats and brains in its environment needed for them to refer to those objects. However, as I said in that first post, for Putnam the BIV argument was just a warm-up exercise. He uses the traditional BIV scenario to illustrate what he regards as the key error of “metaphysical realism” (the view that our percepts and thoughts refer to mind-independent things): that it necessarily relies on a God’s Eye perspective from which we can determine what mind-independent things our percepts and thoughts refer to. Of course, there is no God’s Eye perspective available to human beings, and that is why the project of metaphysical realism must end in failure. Thus, Putnam’s real view is that even if the BIV had the same causal-perceptual embedding in its environment that we enjoy, it would make no difference! Its percepts and thoughts would still not refer to mind-independent things. Reference to mind-independent things is impossible in general. The traditional worry about whether you could be a BIV is a useful entrée to these issues because it presupposes metaphysical realism. Only a metaphysical realist would or could worry about being a BIV, because only if the objects of thought were mind-independent would it be possible to be so radically in error about the nature of one’s environment.

Why does Putnam think that only a God’s Eye perspective can determine the reference of our thoughts and percepts? The reason is given in the so-called “model-theoretic argument” that Putnam presents in each of the three works I mentioned in the first post (“Realism and Reason” [R&R], “Models and Reality” [M&R], and Reason, Truth, and History [RT&H]. In the present post, I explain the argument and the “internal realist” view that Putnam advocates on the basis of it. In the next post, we will examine the merits of the model-theoretic argument. (The whole paper on which these posts are based is available here. To skip to the third post in the series, click here.)

Continue reading →

Could Hilary Putnam Have Been a Brain in a Vat?: Three Arguments against Reference, Part 1

Posted on by under Perception, structural realism

In previous posts (such as this one and this one), I have sometimes alluded to the philosophy of structural realism. Structural realism says that we are unable to know the intrinsic character of the world outside our minds, although we are able to know a great deal about the structure of that world, especially its causally relevant features. Thus, we can know what we need to know to survive and thrive in our environment, we just can’t know what it is like intrinsically. For instance, we cannot know whether the surfaces of objects have the colors they appear to have in our visual perceptions of them or the hot and cold qualities we feel them to have, etc. Even the intrinsic character of spatial relations may not be as it appears to us. Still, the structure and dynamics of all these things is accessible to us—which is fortunate, because that is what matters for successful action.

I think structural realism is true and indeed inescapable. However, discussion of it in philosophy today is blighted by obsession with something called “Newman’s Objection,” after Max Newman, a Cambridge mathematician who published an important critique of Bertrand Russell’s version of structural realism as advanced in Russell’s book, The Analysis of Matter (1927). In my view, Newman rightly identified an important flaw in Russell’s structural realism, but not in structural realism per se, which has many options available for removing the difficulty. Unfortunately, many philosophers today, including many structural realists, treat Newman’s Objection against Russell (and subsequent formulations essentially like Russell’s), unless it can be refuted somehow, as a decisive refutation of structural realism itself. The result has been a lamentable lack of progress in developing the implications and insights of structural realism.

In what follows, I will explain how I think Newman’s Objection should best be handled and why it is a paper tiger. However, I have chosen to do so via an analysis of a much more well-known argument that in its essentials is practically identical with Newman’s, namely Hilary Putnam’s “model-theoretic argument” against the possibility that the terms of natural language or of our thoughts and percepts can have determinate referents in the mind-independent world.

This means that “what follows” is going to be a long haul! If anyone wants to read the whole paper in one fell swoop, it can be found here. Here at PoT, I will send it out in five installments, of which this post is the first. In this first installment, I begin with Putnam’s own warm-up exercise: his argument that a “brain in a vat” would be unable even to think that it was a brain in a vat. (To skip to the second installment, click here.)

Continue reading →