Went to OS review session. New topo homework is sort of annoying. Thoughts on stratifiability: recovering a stratification from just the open sets is relatively easy (and it does seem to need T1 so that each stratum has no accumulation points) but hard to recover it from just the points. Straightforward proof of open stratifiability = metrizability (modulo isolated points) fails because the 'escape velocity' condition isn't quite strong enough to guarantee *uniform* shrinkage of strata elements. T0 + no isolated points => open sets are infinite? Cohen forcing is beginning to make a lot more sense than it once did to me. The topos-theoretic approach is still nowhere near comprehension, though.