I've often wondered how the author of the DOI could rationalize the owning of slaves.

I have said that the Declaration of Independence is the ring-bolt to the chain of your nation’s destiny; so, indeed, I regard it. The principles contained in that instrument are saving principles. Stand by those principles, be true to them on all occasions, in all places, against all foes, and at whatever cost.

— Frederick Douglass, Speech given at Rochester, New York [July 5, 1852]