A form of Social Darwinism.
Hitler's view were actually very similar to Madison Grant and Lothrop Stoddard. The idea that there was one unique aristocratic race that carried "the burden of civilization."
From here he assumes that there's a "natural order" in life devised by Nature. So he replaces God with Nature and religious laws with natural laws that are immutable. Eugenics and blood are actually very similar as well. Since you can interchange the concept of "IQ" with "vitality of blood."
"All the great civilizations of the past became decadent because the originally creative race died out, as a result of contamination of the blood. The most profound cause of such a decline is to be found in the fact that the people ignored the principle that all culture depends on men, and not the reverse. In other words, in order to preserve a certain culture, the type of manhood that creates such a culture must be preserved. But such a preservation goes hand-in-hand with the inexorable law that it is the strongest and the best who must triumph and that they have the right to endure. "-Mein Kampf
Sources: "The Revolt Against Civilization," Lothrop Stoddard. "Mein Kampf," Hitler. "Hitler's second book," Hitler. "Landmark Speeches of National Socialism," Randall L. Bytwerk. "The Passing of the Great Race," Madison Grant