As applied to political practice.
I have seen some remarks from different Socialists which seem to place History and Theory in opposition to each other. History, they say, is what really happened: therefore it is superior to Theory. In so far as the word Theory is often (and unfortunately) used to denote any speculative or unsupported opinions, which have no grounding in experience, the proposition is sound. But it follows from such a definition, that when these Socialists compare History to Theory, they really compare History to drivel—they compare instructive histories to the worst examples of “theory”, opinions which have little or no relation to experience, and which are therefore of no use to anybody.
This is not a just comparison. It would be more apt to place good History next to good Theory, and to place bad History next to bad Theory, before making a judgment as to which of the two is superior. But even this method would be misleading, because History and Theory amount to the same thing, when they are considered as guides to future action.
If I want to learn from a History, in order to apply my knowledge to future situations, I must have some understanding of causes and effects; and I must be able to abstract from the particular historical circumstances to a more general rule. So soon as the reader of a history applies his intellect to identifying these causal sequences, to guide his future action, he becomes a theorist. The framing of general propositions from experience is precisely the work of theory; and the theory is good in so far as it is supported by the evidence of the past. Hence Theory and History are indissolubly connected: we cannot have Theory without History; nor can History be useful to us in practice, without the abstraction of Theory.
What, then, is the distinction between History and Theory, considered as guides to our political action? Supposing that we are comparing like with like—good History with good Theory—they merely differ in emphasis. A good work of history accumulates evidence, correctly identifies causal sequences, and furnishes the material for the production of theories. A good work of theory is founded upon experience, that is, historical evidence, but its object is not to narrate or to explain past events in detail; it is to bring together generalisations, and from these to infer what is likely to happen, and how we should act given our circumstances.
Talal Hangari
Notes in the Margins of the Days 