Please answer a question about the following article about Idealism:

Absolute idealism is G. W. F. Hegel's account of how existence is comprehensible as an all-inclusive whole. Hegel called his philosophy "absolute" idealism in contrast to the "subjective idealism" of Berkeley and the "transcendental idealism" of Kant and Fichte, which were not based on a critique of the finite and a dialectical philosophy of history as Hegel's idealism was. The exercise of reason and intellect enables the philosopher to know ultimate historical reality, the phenomenological constitution of self-determination, the dialectical development of self-awareness and personality in the realm of History.

How did Hegel believe historical reality to be knowable to a philosopher?
exercise of reason and intellect