In this quote, Lukacs identifies a fundamental insight: all knowledge is memory, even the knowledge of the imagination. He calls in an insight of C.S. Lewis to develop this idea:
The past in our minds is memory. Human beings cannot create, or even imagine, anything that is entirely new. (The Greek work for "truth, aletheia, also means "not forgetting")"There is not a vestige of real creativity de novo in us," C.S. Lewis once wrote. No one can even imagine an entirely new color; or an entirely new animal; or even a third sex. At best (or worst) one can imagine a new combination of already existing—that is, known to us—colors, or monsters, or sexes.
At the End of an Age (52).
Lukacs then goes on the quote another favorite of mine, William James:
William James wrote: "You can give humanistic value to almost anything by teaching it historically. Geology, economics, mechanics, are humanities when taught by reference to the successive achievements of the geniuses to whom these sciences owe their being. Not taught thus, literature means grammar, art a catalog, history as list of dates, and natural science a sheet of formulas and weights and measures"
At the End of an Age (53), quoting James, Memories and Studies (1911) (312-313).
Lukacs goes on to summarize this line of thought:
In sum, the history of anything amounts to that thing itself. History is not a social science but an unavoidable form of thought. That "we live forward but we can only think backward" is true not only of the present (which is always a fleeting illusion) but of our entire view of the future: for even when we think of the future we do this by remembering. But history cannot tell us anything about the future with certainly. Intelligent research, together with a stab of psychological understanding, may enable us to reconstruct something from the past; still, it cannot help us predict the future. There are many reasons for this unpredictability (for believing Christians let me say that Providence is one); but another (God-ordained) element is that no two human beings have ever been the same. History is real; but it cannot be made to "work", because of its unpredictability.
At the End of an Age ((53-54)I might add that Lukacs, starting back in the 1960s, took an interest in quantum theory as a metaphor for understanding the historical world. I think that I would bring in complexity theory. History, like the weather, does not submit to predictable certainty, but like climate, we can discern broad outlines of what may likely happen (although now we have man-made climate change to contend with, thus making history even more complex!). See Niall Ferguson's recruitment of complexity theory to explain historical change and causation in his introductory essay to Virtual History.