When the mind became indefensible as the seat of the self — divided by a corpus callosum, altered by a milligram, absent for a third of every day — the position fell back to the body. Whatever else is negotiable, this is mine, it is one, and it is here.

The body: thirty trillion of your cells and roughly the same number that are not, running a metabolism you did not specify; a gut flora acquired at birth and in restaurants, which votes on your appetites; a skeleton being dismantled and rebuilt at about ten per cent a year; mitochondria that are a separate organism you have never met, from a merger before there were animals.

The mass you had at seven is gone. Not metaphorically. It has been excreted. What continues is a pattern of organisation that has never once been made of the same material for two consecutive decades.

This is not a fall. Nothing has been lost. The body was never a possession and the discovery that it is a process is only distressing if you had been quietly relying on it as the deed of title for everything else.

Which you had. Everyone had. That is what makes this a stratum and not an observation.