In a series of posts, I have attempted to infer some of the intellectual sources of key concepts in Rand's Objectivist philosophy. The purpose of these investigations is not to question Rand's originality, or suggest she stole her best ideas from other thinkers, but to emphasize that she had to get her ideas from somewhere. Unless we adopt the supposition, haughtily dismissed by Rand herself, of innate ideas, Rand must have gotten her ideas either through direct observation and/or by contact and interaction with the ideas of others. Now ideas about history, epistemology, social change and the like cannot be made solely through direct observation. They must be formed through contact with ideas found in books and in the conversation with other people. As Rand is not known to have been a volumunious reader, it is likely that she was (perhaps unwittingly) influenced by the intellectuals she conversed with, which, in the thirties and forties, were primarily "conservative" intellectuals, such as Isabel Patterson, Leonard Read, and Henry Hazlitt. All influences, of course, were run through the Randian filter, so they were often transformed into something else by the time Rand got done with them.
Now in Objectivism we can trace two types of ideas: those ideas that are core to Rand's thought and psychopathology and that probably would've remained the same regardless of how she had been influenced; and those ideas that stem from the concepts and notions she found herself exposed to in the intellectual circles in which she travelled. An example of the first type of idea is Rand's support of selfishness, which she stubbornly adhered to despite the protestations of Nathaniel Branden. An example of the second type of idea is her contention that the failure to solve the problem of universals is the main cause of modern irrationality. This notion was, I suspect, suggested by Richard Weaver's central thesis in his book Ideas Have Consequences. Had Weaver not written and published that book, Rand may have never been exposed to the idea of regarding the issue of universals as central to the modern world. And if she had never been exposed to that idea, her theory of history must have taken on a different aspect. She would've had to come up with a different scapegoat for modern irrationality. A different scapegoat, however, would've shifted her focus in epistemology from the issue of universals and concepts to something else. In that case, IOTE would've been a very different book.
So in Objectivism we can trace substantive ideas that find their root in Rand's particular way of thinking and responding to the issues life confronts us with; and then we have ideas that are merely formal and arbitrary, that easily could've been different if Rand had travelled in different intellectual circles and been exposed to different ideas. In the theory of history, the substantive idea is the notion that abstract ideas determine the course of history. Rand's seems to have taken this as an axiomatic idea right from the start. However, the actual form this idea took, the actual abstract ideas that would, for Rand, determine history, was probably determined second or third hand from Richard Weaver, and would've been different had she never been exposed to Weaver's thesis.