People focus on the messenger more than on the message. Jesus preached individual freedom for which he was executed by the Authorities of the time. Now, dare I say, the majority of people who praise Jesus willingly empower the authority of their time to limit individual freedom, while at the same time preaching it.
We can argue that science proves that nothing is certain, but red and white blood cells keep you alive, and that's unlikely to change. We can't live at our current state of output if we didn't take this for granted. Thus, certainties exist at various degrees, and we know that some things work.
In the same spirit, all individuals must assess for themselves how certain are the definitions of the words they use and why, if they are to remain individuals. Freedom cannot mean slavery at the same time, or a little less freedom from the initial meaning of the word. Without these certainties of language, we cannot communicate at level. It would render science impossible. Rand had her issues, and I think The Fountainhead is her best work. Her cult of personality does not do justice to the message.