What are the contradictions made in Alexander Stephen's cornerstone speech?

In Alexander Stephens' Cornerstone Speech, he contradicted himself by stating that the Confederacy was founded on the principle of white supremacy and the inferiority of the African race while asserting that this belief was not a new idea. He also contradicted the Declaration of Independence by arguing that slavery was a foundational and natural institution, despite the Declaration's assertion that all men are created equal.