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Friday, October 22, 2010


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I suspect that you are right that it is not possible to derive knowledge of identity over time based upon induction or based upon qualitative comparison.

But perhaps a Popperian line can be helpful here. First identity is basic: i.e., not reducible to qualitative similarity. Second, suppose that we delineate something from its environment and identify it as a distinct physical object. (I do not have criteria that establish the conditions under which this assumption is justified; perhaps, Strawson's "Individuals" may do so).

Then we assume as a working hypothesis that the object so delineated persists through time unless we encounter evidence to the contrary. That is: given that we have identified something as an object, we proceed with the hypothesis that it persists unless evidence refutes this hypothesis.


If you consider that as we ourselves inhale and exhale, eat and eliminate, we are being changed over the course of a few years in such a way that only a small portion of my previous self actually remains in my current body. Where is the knowledge contained in the every changing set of molecules that is me? Why should I trust this knowledge? But I do.

I guess the time slice business depends on your view of the nature of time, A or B theory. It seems the B theory really messes up the ordinary way we think of sameness.

Didn't you post this same column before?


Why not take an externalist line and say that we know things are identical although that which counts as warrant for our beliefs is "inaccessible" to us?


Your response suggests that identity is an a priori concept that we impose on experience rarher than one we learn a posteriori from experience.


You have a good memory. Some years back a posted a version of this on the old blog. Everything on the old blog will eventually be reposted with modeifications on this one.


I guess I'm an unregenerate internalist. If I know something,it seems quite appropriate to ask how I know it. When I see you again I will know what you are the same person I have met several times before. It seems unsatisfactory and unphilosophcal to be content with saying that that I will just know this.

It's still appropriate to ask how you know a thing on an externalist account; it is just that your answer won't necessarily be other things you belief or nonpropositional evidence you have (like sense perceptions or seemings), but your answer might be "my belief is produced by a reliable belief-forming mechanism" or "my belief is the product of properly-functioning cognitive faculties..."

If you think that all answers to the question, "How do you know?", have to involve evidence like other beliefs or nonpropositional evidence, then it seems we are in the makings for a regress. For surely you know that p only if you believe some bit of evidence E is evidence for p; but your knowledge that p is contingent upon the justification of your belief that E is evidence for p. But then we have another belief that we'll need new evidence to justify -- and you can see the regress that it will set off.

It isn't really the same banana. It is in some sense the descendant of the banana you saw yesterday. But how do you know it is the descendant? How do you know that Descartes' demon didn't switch it's ancestor with a different banana when you blinked?

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