The Declaration asserts that all men are created equal. Lincoln, in the opening words of the Gettysburg Address, speaks of this nation being dedicated to that proposition. But that proposition is not self-evident, because it is not undeniable that God exists or that God created mankind along with other living organisms and everything else in the cosmos. These things may be true. They may be believed.
All men are by nature equal.
For a truth to be self-evident it must be beyond the shadow of a doubt. It must be undeniable simply because its opposite is impossible for us to think. Yes, remarkable as it may seem, a doubt about the existence of human nature has appeared for the first time in our own century. It Is not questioned that other species of animals have specific natures, each thereby having a set of common attributes that differentiate them. I have attempted in another book to expose the error in this view.