Jamieson, Fausset and Brown on Jude 1:10

10. (2Pe 2:12.)

those things which--Greek, "all things whatsoever they understand not," namely, the things of the spiritual world.

but what ... naturally--Connect thus, "Whatever (so the Greek) things naturally (by natural, blind instinct), as the unreasoning (so the Greek) animals, they know," &c. The Greek for the former "know" implies deeper knowledge; the latter "know," the mere perception of the "animal senses and faculties."