Which preposition to use with subtil

in Occurrences 2%

we cannot be too subtil in this business, I say, but how? Bes. Even with his Royal hand.

of Occurrences 1%

He was the farthest reach of subtlety compatible with an individual self,the subtilest of authors, and only just within the possibility of authorship.

than Occurrences 1%

Something keener than philosophy, subtiler than Epicurus, pricked Fred, as Minnie vanished into the cloud of snowflakes.

Which preposition to use with  subtil