In her theory of human nature, Rand made several assumptions important to her epistemology:
(1) That there is nothing in the unconscious (or "subconscious") that is not acquired by conscious means. Orthodox Objectivism is rather inflexible in its view on this matter. Leonard Peikoff, during the Q & A of his lectures on Objectivism (and in the presence of Ayn Rand), explained the Objectivist position as follows:
Objectivism does not subscribe to the idea of an unconscious at all. We use the term “subconscious” instead—and that is simply a name for the content of your mind that you are not focused on at any given moment. It is simply a repository for past information or conclusions that you were once conscious of in some form, but that are now stored beneath the threshold of consciousness. There is nothing in the subconscious besides what you acquired by conscious means. The subconscious does perform automatically certain important integrations (sometimes these are correct, sometimes not), but the conscious mind is always able to know what these are (and to correct them, if necessary). The subconscious has no purposes or values of its own, and it does not engage in diabolical manipulations behind the scenes. In that sense, it is certainly not “dynamic.”
This view of subconscious (i.e., unconscious) mental processes is simply wrong. Empirical psychology has discovered that consciousness is merely the tip of the iceberg, and that the "adaptive" unconscious plays a much larger role in cognition and decision making than most people realize:
Some of Freud’s ideas [about human unconscious] have been verified, at least in a general sense. For example, one of the basic premises of psychoanalysis — that people possess unconscious defensive processes that protect their self-esteem — has been well established. But Freud’s view of an infantile, primitive unconscious has proved to be far too limited; the unconscious is much more sophisticated and powerful than he imagined. Humans possess a powerful set of psychological processes that are critical for survival and operate behind the conscious mental scene.
These processes, called the “adaptive unconscious,” are intimately involved in how we size up our world, perceive danger, initiate action, and set our goals. It is the unconscious that allows us to learn our native language with no conscious effort, recognize patterns in our environments while we think about something else, and develop reliable intuitions to guide our actions.
While consciousness may, to some degree, affect the adaptive unconscious, Objectivism's extreme view declaring that the conscious mind can always know what goes into the unconscious mind is not warranted by the facts. Indeed, the evidence, if anything, seems to to suggest that the opposite view may be closer to the truth, and that the conscious mind plays far less of a role in cognition and decision making than personal experience suggests. Experimental psychologists have discovered what they call the "introspective illusion," defined as
a cognitive bias in which people wrongly think they have direct insight into the origins of their mental states, while treating others' introspections as unreliable. In certain situations, this illusion leads people to make confident but false explanations of their own behavior or inaccurate predictions of their future mental states.
In other words, not only is Objectivism wrong about the unconscious mind, it also adheres to an illusory belief about introspection. Rand believed that with "a ruthlessly honest commitment to introspection," individuals could discover not only what they feel, but what aroused that feeling and whether that "feeling is an appropriate response to the facts of reality."
The evidence from experimental psychology strongly suggests that Rand's view of introspection is mistaken, that the mind has no direct access to underlying mental states and that what Rand calls introspection is often mere confabulation.
Rand's erroneous view of the unconscious mind and introspection upends her entire epistemological project. Critical to this project is Rand's belief that one's mental processes have to be validated. For example, her theory of concepts attempts to "validate" conceptual knowledge. However, as most (if not all) concepts are formed by unconscious process not available to introspection, Rand's insistence that such processes need to be consciously validated would constitute a false ideal. Rand's mania for validating processes of knowledge would appear to be entirely vain endeavor, not merely wrong, but utterly irrelevant.
(2) Reason is the only valid (i.e., efficacious) means of attaining knowledge. This view is critical not merely to Rand's epistemology, but to her ethics and politics as well. It is almost certainly wrong. Even if we ignore the vagueness of Rand's conception of reason, cognitive science has discovered that the unconscious mind plays a much larger role in cognitive processes than previously imagined. Much of our thinking occurs below the threshold of consciousness. Much of our thinking is intuitive and tacit, rather than conscious or explicit. Thinking and memory operate on two, interacting levels: the conscious/deliberate and the unconscious/automatic. Each of these two levels have their strengths and weaknesses, making them better or worse depending on specific cognitive challenges. But it is simply not true, as Rand seems to be suggesting, that "reason" (i.e., the conscious/deliberate level of thinking), is the only efficacious method. Rand's error on this issue leaves an immense hole in her philosophy.
(3) Human behavior is affected by philosophical issues. Rand's views on the "importance" of philosophy are widely known among her followers, but their source in Rand's theory of human nature often goes unappreciated, while their implications for her epistemology are usually ignored. Rand stated her position as follows:
As a human being, you have no choice about the fact that you need a philosophy. Your only choice is whether you define your philosophy by a conscious, rational, disciplined process of thought and scrupulously logical deliberation—or let your subconscious accumulate a junk heap of unwarranted conclusions, false generalizations, undefined contradictions, undigested slogans, unidentified wishes, doubts and fears, thrown together by chance, but integrated by your subconscious into a kind of mongrel philosophy and fused into a single, solid weight: self-doubt, like a ball and chain in the place where your mind’s wings should have grown.I want to focus here on Rand's conclusion: namely, that if your philosophy is produced, not by rational disciplined thought, but by chance, the result is self-doubt and a mind incapable of reaching its full potential. This constitutes a further refinement of Rand's view of the subconscious. It provides at least partial justification for a doctrine essential to her epistemology — namely, foundationalism. Since self-doubt cripples man's mind, it has to be combated in all its many incarnations. For Rand, one of the most important functions of philosophy is to "validate" man's mind and values. In the absence of this validation, man loses confidence in his conscious, rational mind and gives way to the self-doubt promoted by a "mis-integrated" subconscious. In other words, Rand believes that human beings are so constituted as to require validation of the efficacy of their minds if they are to reach their full potential.
Of course, this aspect of human nature is merely implicit in Objectivism. It's unclear whether Rand thought out all the implications of her view concerning the importance of validation. Rand's mania for validation only seems to make sense if we assume that the need to justify man's mind arises from innate tendencies. But as we know, Rand denied the existence of all such tendencies, so it's not clear why validation should be so very important, since by changing premises you could conceivably create individuals who believed in the mind's efficacy without being uptight about validation.
In any case, there is little if any evidence supporting Rand's contention that human beings require validation of their minds in order to avoid the perils of skepticism and self-doubt. Sincere skepticism is actually rather rare. Most people are rather intense and unyielding dogmatists. If they occasionally veer into skepticism, it's usually about issues they don't care much about, or about views they disagree with. People are rarely skeptics about their core religious and/or ideological beliefs. Self-doubt, when it exists at all, is usually focused on a specific domain. An individual may experience self-doubt in regards to his career or his role as a parent. It rarely extends to his ethical or political beliefs. If person experiences self-doubt over whether they are good person, this does not mean they doubt their ethical beliefs, but rather they doubt whether they are living up to those beliefs.
All this should be obvious from common observation. When was the last time you heard someone say, I used to believe murder and stealing from widows and orphans was wrong, but now I doubt whether I was right? How often do ideological pundits admit they might be wrong about their core political beliefs? How often do religious fundamentalists express skepticism concerning God's existence, or the truth of their often grossly implausible theological opinions? Skepticism about such matters is rare, except among those with opposing opinions. Moreover, skepticism, when it does make an appearance, is often little more than a form of etiquette: a tactic used to avoid futile arguments with raving dogmatists. Skepticism is hardly the bogeyman that Rand and her disciples make it out to be; nor is foundationalism necessary to prevent human beings from the horrors of self-doubt and a "mis-integrated" consciousness. Most human beings are entirely indifferent to such recondite issues as the validity of concepts or the problem of induction. Even if (per implausible) these things could be "validated," most people would be incapable of appreciating, let alone understanding, the issues involved.