“History therefore is a process of selection in terms of historical significance. To borrow Talcott Parsons’s phrase once more, history is ‘a selective system’ not only of cognitive, but of causal, orientations to reality. Just as from the infinite ocean of facts the historian selects those which are significant for his purpose, so from the multiplicity of sequences of cause and effect he extracts those, and only those, which are historically significant; and the standard of historical significance is his ability to fit them into his pattern of rational explanation and interpretation.”