Rosenberg's racial interpretation of history concentrates on the negative influence of the Jewish race in contrast to the Aryan race. He equates the latter with the Nordic peoples of northern Europe and also includes the Berbers from North Africa and the upper classes of Ancient Egypt. According to Rosenberg, modern culture has been corrupted by Semitic influences (cf. anti-Semitism), which have produced degenerate modern art, along with moral and social degeneration. In contrast, Aryan culture is defined by innate moral sensibility and an energetic will to power. Rosenberg believed that the higher races must rule over the lower and not interbreed with them, because cross-breeding destroys the divine combination of physical heredity and spirit. He uses an organic metaphor of the race and the State and argues that the Nazis must purify the race soul by eliminating non-Aryan elements in much the same ruthless and uncompromising way in which a surgeon would cut a cancer from a diseased body.