The Tautological Fallacy
By Bryan Caplan
I’m saying that your mind is literally a signal processing
system. Not just metaphorically; literally. That is, while minds have a
great many features, a powerful theory, in fact our standard theory, to
explain the mix of features we see associated with minds, is that minds
fundamentally function to process signals, and that brains are the
physical devices that achieve that function. And our standard theories
of how physical devices achieve signal processing functions predicts
that we can replicate, or “emulate”, the same signal processing
functions in quite different physical devices. In fact, such theories
tell us how to replicate such functions in other devices…
[G]iven how rich and well developed are our standard theories of
minds as signal processors, signal processors in general, and the
implementation of signal processors in physical hardware, it hardly
seems fair to reject my conclusion based on a mere “metaphor.”
Unfortunately, the best possible response isn’t good enough. The “standard theories of minds as signal processors” that Robin refers to aren’t theories at all. They’re just eccentric tautologies.
As Robin has frankly admittedly to me several times, he uses the term “signal processors” so broadly that everything whatsoever is a signal processor. On Robin’s terms, a rock is a signal processor. What “signals” do rocks “process”? By moving or not moving, rocks process signals about the mass and distance of other objects in the universe. By warming or cooling, rocks process signals about the energy and distance of other objects in the universe. Etc. Woh.
The only way Robin can avoid the Metaphorical Fallacy, then, is to commit what I’ll call the Tautological Fallacy. Here’s how it works:
1. Define a concept Y such that all conceivable things are Y. (It’s rhetorically most effective to begin with a somewhat familiar semi-technical term like “signal processing,” then eccentrically redefine it).
2. Trivially infer that X is Y.
3. Claim this implies something substantive about X.
This is intellectual sleight of hand. Once you define every conceivable thing to be a signal processor, being a signal processor does not and cannot have any substantive implications. You can “upload a human mind to a computer” in the same trivial sense that you can “upload a rock to a computer” or “upload a rock to a human mind.” Anyone who thinks such sophistry is a path to personal immortality is sadly mistaken.