Over the last couple of years, cryonics pioneer Robert Ettinger has been a vocal critic of simplistic defenses of the idea of mind uploading as a survival strategy. He has worked out his reservations in detail in his latest book Youniverse: Toward a Self-Centered Philosophy of Immortalism and Cryonics. In a recent CryoNet message he reiterates some of his basic arguments:

“Identity of indiscernibles” is a  common tenet. Often attributed to Leibniz, one  version is that if two physical objects or systems cannot be distinguished from  each other by any criterion, then they  must be considered the “same” or  identical. First, this assertion actually asserts nothing except a  certain preference in use  of language. It has no consequences. It is also useless because if the question arises, are A and B distinguishable, the answer  is always yes.

It is hard to see how anyone can claim complete certainty  on the topic of mind uploading. Nevertheless, to some of its more dogmatic advocates the case for mind uploading is simply an exercise in deductive reasoning. There are major objections to such an attitude. The most obvious point is general; why should mind uploading be an exception to the rule that we can have no certain knowledge? One might object that absolute certainty is possible in logic. But in that case one would need to defend the thesis that the feasibility of mind uploading (and its associated views about identity) is a purely logical matter and exempt from empirical testing. This is not a credible position.

This does not mean that questions about identity will be easily answered when such technologies are available. For all we know, mind uploading will be technically feasible and the debates about identity continue.  There is a lot of merit to discussions about mind uploading and identity, especially for those interested in cryonics and life extension. But there is also a lot to say for being modest in making bold claims before such technologies have materialized.