The Communists claim that they are the champions of reason and science. If the Conservatives concede that claim and retreat into the realm of religion, it will be an act of intellectual abdication, the kind of intellectual surrender that the Communists’ irrational ideology could never have won on its own merits.
The conflict between Capitalism and Communism is a philosophical and moral conflict, which must be fought and won in men’s minds, in the realm of ideas; without that victory, no victory in the political realm is possible. But one cannot win men’s minds by telling them not to think; one cannot win an intellectual battle by renouncing the intellect; one cannot convince anybody by appealing to faith.
Capitalism is perishing by default. The historical cause of its destruction is the failure of its philosophical advocates to present a full, consistent case and to offer a moral justification for their stand. Yet reason is on the side of Capitalism; an irrefutable rational case can be, and must be, offered by its defenders. The philosophical default of the Conservatives will become final, if Capitalism—the one and only rational way of life—is reduced to the status of a mystic doctrine.
I am not suggesting that you should take a stand against religion. I am saying that Capitalism and religion are two separate issues, which should not be united into one “package deal” or one common cause. This does not mean that religious persons cannot crusade for Capitalism; but it does mean that nonreligious persons, like myself, cannot crusade for religion.
source ... June 4, 1960 Letter to Barry Goldwater, Letters of Ayn Ran