A common point when it comes up is that although Rand used the technical language of philosophy, she did not write with analytical rigor, she misused the language and nor did her use of the terminology express a clear meaning. You can see this in almost any conversation with an objectivist as they will constantly throw in philosophical sounding sentences like “egalitarianism cannot be applied as a metaphysical principle” and if you are familiar with philosophy you will think “well of course not” because the sentence doesn’t make sense.
In other areas Objectivism uses the language correctly but comes to obviously erroneous conclusions. Let me quote from Introduction to objectivist epistemology:
Any theory that propounds an opposition between the logical and the empirical, represents a failure to grasp the nature of logic and its role in human cognition. Man’s knowledge is not acquired by logic apart from experience or by experience apart from logic, but by the application of logic to experience. All truths are the product of a logical identification of the facts of experience
Basically, the above is denying the existence of a priori knowledge by claiming that no knowledge is possible without experiencing some phenomenon and then analyzing it logically. However, an obvious contradiction is the fact that numbers do not exist as objects which one can experience and yet without ever even having heard of any particular equation one can deduce a necessarily true answer. However, if experience is a necessary component of knowledge then even an elementary deduction such as 3(x2 +5) = 3x2 +15 (or even A=A, as she loved to say) is unknowable, as what would it mean to “experience” an equation? More simply stated, numbers do not exist as “real” things in reality and we cannot experience them, yet we can certainly multiply and divide. Another example, and one that is more famous, is “all bachelors are unmarried men,” a statement which is true by definition and requires no empirical testing.
Here is another claim on the same subject which is seriously at odds with reality, from The anti-industrial revolution:
[Man] is born naked and unarmed, without fangs, claws, horns, or “instinctual knowledge.”
This echoes the claim from above but the flaw is a bit more obvious when considering our understanding of evolutionary theory. Rand believed that people were born “tabula rasa,” or with a blank slate and that no knowledge was innate. Basically, to believe it true that humans have no instinctual knowledge, one must believe that animal brains evolved over millions of years to use instinct but that it somehow disappeared in humans and was immediately replaced with pure reason. I’m not sure how familiar you are with evolutionary theory but if you understand the basics you can see how glaringly obvious the problem is (and if not then I’m happy to elucidate). If we don’t have instinct and if all knowledge is conceptual then I’m a serious loss to explain how a human baby mimics mammals of other species by instinctively knowing how to feed on its mother’s breast. One would have to believe that even though the puppy and human infant are both mammals with a shared evolutionary history, engaging in the same behavior, it’s just a big coincidence.
Now to get back to why Rand is ridiculed. Rand is ridiculed because the above objections to a single paragraph and one sentence are obvious to any philosophy undergrad worth his or her salt (and there are other problems as well that I left out to save you from boredom). It is not simply that she was wrong, but that she was obviously wrong.
Her work is seductive to some laymen – especially those of the right-wing persuasion – but to a trained philosopher or logician or anyone with critical thinking skills… it’s fairly obvious that it’s comprised mostly of fallacies (mostly argument by assertion) and cult-like repetition. In other words, Rand is to philosophy what Glenn Beck’s “lecture” segment is to political science. Or put it more aptly, Rand is to philosophy as Rand is to literature.