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Cognitive Scientist, UC, Irvine; Author, Visual Intelligence
A spoon is like a headache

A spoon is like a headache. This is a dangerous idea in sheep's clothing. It consumes decrepit ontology, preserves methodological naturalism, and inspires exploration for a new ontology, a vehicle sufficiently robust to sustain the next leg of our search for a theory of everything.

How could a spoon and a headache do all this? Suppose I have a headache, and I tell you about it. It is, say, a pounding headache that started at the back of the neck and migrated to encompass my forehead and eyes. You respond empathetically, recalling a similar headache you had, and suggest a couple remedies. We discuss our headaches and remedies a bit, then move on to other topics.

Of course no one but me can experience my headaches, and no one but you can experience yours. But this posed no obstacle to our meaningful conversation. You simply assumed that my headaches are relevantly similar to yours, and I assumed the same about your headaches. The fact that there is no "public headache," no single headache that we both experience, is simply no problem.

A spoon is like a headache. Suppose I hand you a spoon. It is common to assume that the spoon I experience during this transfer is numerically identical to the spoon you experience. But this assumption is false. No one but me can experience my spoon, and no one but you can experience your spoon. But this is no problem. It is enough for me to assume that your spoon experience is relevantly similar to mine. For effective communication, no public spoon is necessary, just like no public headache is necessary. Is there a "real spoon," a mind-independent physical object that causes our spoon experiences and resembles our spoon experiences? This is not only unnecessary but unlikely. It is unlikely that the visual experiences of homo sapiens, shaped to permit survival in a particular range of niches, should miraculously also happen to resemble the true nature of a mind-independent realm. Selective pressures for survival do not, except by accident, lead to truth.

One can have a kind of objectivity without requiring public objects. In special relativity, the measurements, and thus the experiences, of mass, length and time differ from observer to observer, depending on their relative velocities. But these differing experiences can be related by the Lorentz transformation. This is all the objectivity one can have, and all one needs to do science.

Once one abandons public physical objects, one must reformulate many current open problems in science. One example is the mind-brain relation. There are no public brains, only my brain experiences and your brain experiences. These brain experiences are just the simplified visual experiences of homo sapiens, shaped for survival in certain niches. The chances that our brain experiences resemble some mind-independent truth are remote at best, and those who would claim otherwise must surely explain the miracle. Failing a clever explanation of this miracle, there is no reason to believe brains cause anything, including minds. And here the wolf unzips the sheep skin, and darts out into the open. The danger becomes apparent the moment we switch from boons to sprains. Oh, pardon the spoonerism.