In Book 11 of the Confessions, Augustine writes, “Are the present hundred years a long time? But first see whether a hundred years can be present. If it is the first year of the hundred, then that year is present, but the other ninety-nine are still in the future, and so as yet are not; if we are in the second year, then one year is past, one year is present, the rest future. Thus whichever year of our hundred-year period we choose as present, those before it have passed away, those after it are still to come. Thus a hundred years cannot be present.”

Is the chosen year itself present? Not wholly: We’re in some particular month, and the other months are not present. And so on — Augustine applies the same argument to days, hours, and even “fleeting moments.” In the end, “If we conceive of some point of time which cannot be divided even into the minutest parts of moments, that is the only point that can be called present: and that point flees at such lightning speed from being future to being past, that it has no extent of duration at all. For if it were so extended, it would be divisible into past and future: the present has no length.”

It sounds straightforward to imagine being another person, but is it? If I want to imagine being Napoleon, I need to conceive some relation between our two identities. If I only imagine some situation that was faced by Napoleon, then the result involves too little of my own identity — I’m not really involved at all. But if I imagine myself in Napoleon’s place, then the result involves too little of him. It doesn’t seem possible for two people to share an identity in this way.

Philosopher Bernard Williams writes, “Leibniz, perhaps, made something like this point when he said to one who expressed the wish that he were King of China, that all he wanted was that he should cease to exist and there should be a King in China.”

But, Williams says, it does seem possible to play a role, to pretend to be Napoleon. In that case my first-person thoughts are framed in another’s point of view, so the identity of “I” is less problematic. In this sense perhaps I can imagine being Napoleon — but not having been Napoleon.

(Bernard Williams, Problems of the Self, 1976.)

In 1988, tunneling operations began in both England and France. On Dec. 1, 1990, these two single-entrance holes met under the English Channel, after which there existed a two-entrance tunnel. The completed Channel Tunnel would not be ready for use until 1994. Now, suppose that a speaker in 1989 had said:

There is in the process of coming into existence, so we understand, the Channel Tunnel. Not many of us have seen it; I certainly have not. One understands that that will allow us, if and when it is made available, to travel by train from England to France.

Does this utterance imply that, at the time it was spoken, the Channel Tunnel already existed? If not, what is the it that the speaker says few people have seen? In 1989 all that existed were two blind tunnels, which together could not permit free passage between England and France, surely an essential feature of the Channel Tunnel.

“In the construction of the Channel Tunnel, the time at which we can say that a two-entrance tunnel first exists is 1st December 1990, when the two one-entrance tunnels met,” notes philosopher Antony Galton. “The Channel Tunnel is a two-entrance tunnel; so is this time, 1st December 1990, also the time at which the Channel Tunnel first exists?”

(Antony Galton, “On the Process of Coming Into Existence,” Monist 89:3 [July 2006], 294-312.)