Von Ranke's school of historiography is based on the idea of wie es eigentlich gewesen, the idea of writing history as it actually happened. This means historians must remove themselves of all bias while writing. Other historians, such as Charles A Beard, have argued that it is impossible for the writer to remove themselves of their beliefs and biases. He was also a pioneer in the idea of empiricism in the school of history. Facts , evidence and sources became important to the school of historical thought after von Ranke.