In W. H. Walsh's widely read book, An Introduction to the Philosophy of History (1951) there is set out a distinction which became virtually classic, or canonical, between two kinds of philosophy of history. On the one hand, there is critical philosophy of history, which investigates, in what is supposed to be a more or less neutral and objective way, the actual practices of historians, with a view to determining their methods, the character of their cognitive and explanatory claims, resemblances to other kinds of inquiry, differences, and other matters of allied type. Critical philosophers of history are supposed to have a relation to their subject at least similar to that of philosophers of science to theirs. Walsh approved of critical philosophy of history, and pointed to directions of its future progress. On the other hand, there is speculative philosophy of history, which seeks to give philosophie content and structure to the actual course of history, typically, world history. This was the sort of thing engaged in by people like Hegel, and Auguste Comte, and Spengler and Toynbee; Walsh did not approve of it at all. Walsh's distinction, and similar if different perspectives on it, appear among other places in William Dray's Philosophy of History and in articles on philosophy of history in the Encyclopedia of Philosophy.