Many transhumanist ideas are products of fertile and creative imaginations. Some people would add “unhampered by the normal constraints of scientific and philosophical discipline”. Is that so? My answer: NO, or at least not necessarily.
The history of science and engineering show that in some case it is (e.g. perpetual motion machines), and in some cases it is not (e.g. heavier than air flying machines).
A perpetual motion machine is not compatible with the basic laws of physics as they are understood today. This has also been claimed for heavier than air machines, but in that case the claim was wrong.
The history of science and engineering shows that, if something is logically and physically possible, and if there is sufficient demand for it, it will probably be achieved at some point.
Given a highly imaginative engineering project, we have to choose whether to take it seriously as an airplane, or to dismiss it as a perpetual motion machine. This choice depends of course on many factors, including of course scientific and technical knowledge and experience, but also including many unspoken and at times unconscious assumptions, often emotional in nature, about our reality.
Let’s come now to the “superlative” examples.
One of the assumptions I make is that there is no such a thing as “supernatural” - everything in the universe can be, in principle, analyzed by science. According to this assumption, I think our bodies and minds are machines: very complex machines that are not presently understood in great detail, but nonetheless machines whose detailed blueprint can be in principle known, reproduced and improved. There is no mysterious “vital force” or supernatural “essence” forever beyond the domains of scientific analysis and engineering tinkering.
I also assume that I am the information encoded in my brain. Why? Simple - because I don’t see what else I might be. It seems to me that any other assumption would fall into mystic, magic, and supernatural realms that are completely foreign to my basic assumptions about reality.
On the basis of this assumption and conclusion, I think someday we will be able to upload human personalities to suitable computational supports, much longer lived than biological brains. This is, I believe, fully compatible with our current scientific understanding of the universe.
Of course, opinions about development timescales may differ. Ray Kurzweil sees it happening in only a few decades, while other thinkers believe it cannot take less than thousands of years. My own forecast, based only on my engineering intuition and understanding of current developments, is somewhat intermediate: I imagine operational mind uploading technology deployed by the end of this century or in the next century.
This makes me happy for my grandchildren, who will live in a very interesting world, but I don’t see mind uploading developed during my lifetime. So, on the basis that any finite probability is better than zero, I am signed up for cryonic suspension. The “natural vs. supernatural” argument above tells me that cryonics works in principle - there is no mystic “soul” that irretrievably leaves a frozen brain after death by decree of god.
Does it work in practice? Of course I don’t know. I could die in a plane crash without any possibility to retrieve the brain. Or the brain could not reach the cryonic facility in useful time because of legal complications. Or the current cryonic suspension technology could not be suitable. Or the cryonic facility could be bombed by terrorists. Or…
But, on the basis of the considerations above, I am quite willing to try. Actually I think that the odds are not that good (there many things that can go wrong, so there is a high probability that something will go wrong), but a small probability of surviving death is better than no probability of surviving death. Surviving temporary death by cryonics may permit reaching a future where mind uploading technology can provide a much longer life.
And I think the future could be a beautiful and interesting place. Of course it could also be a very ugly place but, one thing is sure, it will be what we make of it. The possibility that I could live to see it gives me hope, energy and drive.
Summary of this long post: I agree that we should not sell unscientific snake-oil, but I think a very long and interesting life enabled by mind uploading technology, and cryonics as a bridge to reach a point in time where this option is available, is an engineering project compatible with our current scientific knowledge. I do not intend to sell this a certainty, but I do intend to propose it as a possibility.