Simply, Virchow was a determinist. He believed that life could ultimately be reduced to a set of physical laws, like mechanics, and that man's reason could therefore someday penetrate and explain all its mysteries. Consequently, he regarded the course of human history as being one of overall enlightenment, and he desired both as a scientist and as a political thinker to be a part of that process, of finding out what was true and ridding from men's minds what wasn't.
Uyterhoeven, on the other hand, was a vitalist. He recognized life to be a fundamentally spontaneous and creative phenomenon, subject to no law beyond an apparently indomitable will to grow and to ex-pand. Physics and chemistry did well to record her habits, in other words, but provided no explanation as to the vital force which still evidently charged the universe.

Brooks Hansen, The Chess Garden