In the sleep cycles there are two main stages, non-REM sleep and REM sleep.
If y is an infinity, rem returns x.
New babies have extremely short sleep cycles, or periods of deep, light and REM sleep.
I prefer an alternative derivation from Latin " rem legere " meaning the " right thing " that one has to choose.
At the same time he has nothing to say against the Platonic theory of universalia ante rem (see Idealism).