The deplorable perversion of knowledge.
This verse is a practical application of the historic reference to the archangel Michael.
I. THE LESSON OF IGNORANT DEPRECIATION. "But these rail at whatsoever things they know not." These were unseen spiritual powers whom they treat with mocking irreverence.
1. The ignorance in question is that conceited and contented ignorance of which the psalmist speaks. "They know not nor will understand, but walk on in darkness.'' They are "willingly ignorant" (Romans 1:28). None are so ready to speak as the ignorant. Or, it is ignorance of things not possible for man to know in his present life, and is therefore excusable.
2. The sinfulness of railing at such things.
3. It is great wickedness; for it is to impute evil where none may exist. It is to rejoice in the evil which may only exist in our own thoughts. How great is the sin of railing at things which are worthy! We see how corrupt affections blind the judgment.
4. We ought to reprove known evil, and to praise what we know to be good.
II. THE LESSON OF THE RUIN WROUGHT BY SENSUAL KNOWLEDGE. "And what they understand naturally, like the creatures without reason, in these things they corrupt themselves."
1. The range and scope of natural knowledge. Jude refers here to the familiar objects of sense as equally obvious to both man and beast.
2. The corruption that springs out of mere things of sense.