Which preposition to use with verifiable

in Occurrences 1%

They accept, for example, the testimony of others in matters of fact, and their mental results in those subjects with which such men are conversant, on the ground of a just faith in average human capacity in its own sphere; and, in particular, they accept provisional opinions, especially such as are alleged to be verifiable in action, and they put them to the test.

Which preposition to use with  verifiable