Suppose we cryogenically preserve ourselves. Even if our descendants revive us there is a chance that our minds will be too primitive to be properly rebooted. Future technologies may be incompatible with our archaic mind files. It would be as if we found an old floppy disk or early telephone but no longer had the means to run them.

Alternatively, our descendants might reboot our mind files but find that our restored minds cannot deal with a radically different future. In response, our offspring might download their knowledge into our minds, so as to better prepare us for their new world, but find our memory capacity and processing speed insufficient to deal with the procedure. It might kill us to assimilate all their knowledge. Literally.

To handle all this new experience and information our progeny could re-engineer our brains or create new ones for us. Either way, it is hard to see how our personal identity survives. Once we have thirty-first-century brains loaded with thirty-first-century knowledge, we are thirty-first-century beings. And with psychological continuity lost, personal identity would be lost too.

To solve this problem our new brains could be engineered so that we have access to our old mind files—thereby preserving something of our personality. But even if we could occasionally enter our old minds, we might find these former experiences so primitive that we wouldn’t want to remember them. Why remember being a twenty-first-century hominoid when better experiences are available?

So our futures selves, operating on new substrates, would stand in relation to our current selves as we now do to the starstuff. We came from the stars but we are not stars.  At some point, our past lives would be so distant and unfamiliar that our connection with them would be lost. So “we” can’t live in the future. We live, if we live at all, in this reality, in this time. And when that time ends, we will be gone.

And yet …  we do live in the future … in a sense. When we imagine it, when we long for it, we are, to some extent, there. No, our little egos will not be there, that is a triviality best discarded. But as long as minds freely roam space and time we live on—within other minds. This may not be all we want, but it may be all we can get. No one expressed these sentiments as well as Bertrand Russell in his essay “How To Grow Old.”

The best way to overcome it [the fear of death]—so at least it seems to me—is to make your interests gradually wider and more impersonal, until bit by bit the walls of the ego recede, and your life becomes increasingly merged in the universal life. An individual human existence should be like a river: small at first, narrowly contained within its banks, and rushing passionately past rocks and over waterfalls. Gradually the river grows wider, the banks recede, the waters flow more quietly, and in the end, without any visible break, they become merged in the sea, and painlessly lose their individual being. The man who, in old age, can see his life in this way, will not suffer from the fear of death, since the things he cares for will continue. And if, with the decay of vitality, weariness increases, the thought of rest will not be unwelcome. I should wish to die while still at work, knowing that others will carry on what I can no longer do and content in the thought that what was possible has been done.