Followup to: On Being Decoherent

Decoherence is implicit in quantum physics, not an extra postulate on top of it, and quantum physics is continuous. Thus, "decoherence" is not an all-or-nothing phenomenon—there's no sharp cutoff point. Given two blobs, there's a quantitative amount of amplitude that can flow into identical configurations between them. This quantum interference diminishes down to an exponentially tiny infinitesimal as the two blobs separate in configuration space.

Asking exactly when decoherence takes place, in this continuous process, is like asking when, if you keep removing grains of sand from a pile, it stops being a "heap".

The sand-heap dilemma is known as the Sorites Paradox, after the Greek soros, for heap. It is attributed to Eubulides of Miletus, in the 4th century BCE. The moral I draw from this very ancient tale: If you try to draw sharp lines in a continuous process and you end up looking silly, it's your own darn fault.

(Incidentally, I once posed the Sorites Paradox to Marcello Herreshoff, who hadn't previously heard of it; and Marcello answered without the slightest hesitation, "If you remove all the sand, what's left is a 'heap of zero grains'." Now that's a computer scientist.)

Ah, but what about when people become decoherent? What of the Conscious Sorites Paradox?

What about the case where two blobs of amplitude containing people are interacting, but only somewhat - so that there is visibly a degree of causal influence, and visibly a degree of causal independence?

Okay, this interval may work out to less than the Planck time for objects the size of a human brain. But I see that as no excuse to evade the question. In principle we could build a brain that would make the interval longer.

Shouldn't there be some definite fact of the matter as to when one person becomes two people?

Some folks out there would just say "No". I suspect Daniel Dennett would just say "No". Personally, I wish I could just say "No", but I'm not that advanced yet. I haven't yet devised a way to express my appreciation of the orderliness of the universe, which doesn't involve counting people in orderly states as compared to disorderly states.

Yet if you insist on an objective population count, for whatever reason, you have Soritic problems whether or not you delve into quantu...

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