 With respect to existence, however, the ideal factors are powerless. They cannot on their own accord realize any idea or value. Their power lies in their ability to direct and channel the real factors of history. They are parasitic in this manner upon the real factors, having power only in so far as they are able to determine the course of the real factors. The life drives are what gives spirit its power to exist. History, therefore, takes place through the interplay of the real and the ideal factors. Its course is determined by which ideas and values become dominant in directing the life drives.