“One of the greatest distortions [of social analysis] views [historical phenomenon] as the consequences of certain logical interpretations of scripture or other reasonings of the kind.”
Influence of religious doctrine on conduct. All kinds of contradictory behavior find justifications in religious ideas, often even from the same religion. There are Christian pacifists and Christian warriors (e.g., Cromwell’s ironsides); there are Christian apologists for slavery and Christian abolitionists; there are Christian socialists and Christians for the free market. And it is not merely the case that people who identify themselves as Christians fall on either side of these questions; that their Christianity, in other words, is entirely fortuitous. Not at all; they all justify their positions by claiming that they arrived at it by reading scripture. Slave owners claimed that slavery is defended in the Bible; abolitionists claimed that, since each individual is made in the image of God, Christianity demands the end of slavery. It is truly amazing how every position under the sun can be justified by the New or Old Testament. Even entirely contradictory positions!
Christianity is not alone among religions in having this curious power. Indeed, many belief systems, whether religious or secular, seem to share this kind of flexibility, as was noted by Vilfredo Pareto in his immensely fascinating Mind and Society. Pareto made a point of studying the extent to which explicit belief systems, whether religious or metaphysical or ethical in nature, actually determine conduct. Pareto, in his researches, could discover little if any causal connection between explicit belief systems and conduct. People engage in conduct and then use casuistry to defend this conduct on the basis of their stated convictions. After observing this, Pareto decided that it would be foolish to regard the conduct as being merely a logical consequence (or practical application) of the beliefs. Since the same conduct can spring from diametrically opposed beliefs, the beliefs can hardly be regarded as the cause of the conduct. Christianity hardly caused both slavery and the abolition of slavery! So some other causative agent or motivational complex must be at work here. Pareto believed that the primary cause of conduct was innate psychological states (sometimes referred to as “sentiments”) which he called “residues.” The belief systems which were used to justify these residues Pareto called “derivations.” Pareto contended that residues were the primary causes of conduct, particularly “non-logical” conduct, which he studied in great detail. Deriviations were, in comparison, much less important. As he wrote:
The main error in the thinking of the plain man, as well as in metaphysical thinking, lies not only in an inversion of terms in the relationship between derivations and human conduct—the derivation being taken, in general, as the cause of the conduct, whereas really, the conduct is the cause of the derivation—but also in ascribing objective existence to derivations proper and to the residues in which they originate. 
Pareto did not deny that derivations can affect behavior as a secondary cause, by, for example, intensifying the underlying residues. But he would have regarded the Objectivist conviction that the social order is caused by philosophy as hopelessly naive.
In the light of the historical facts illustrated by Pareto’s theory, what are we to make of the actual, real world influence of a religion like Christianity in contemporary America? If we dislike Christianity, we will tend to focus every bad thing done by Christians or in the name of Christianity. If we like Christianity, we will tend to commit the opposite error of focusing on all the good things done by Christianity and Christians. Neither approach does complete justice to the facts, because neither attempts to separate that which is caused by the residues (i.e., religious sentiments) from that which is caused by the derivations (i.e., Christian doctrine).
The situation is rendered even more thorny and complex by the type of relationships that exist between Christian doctrine and Christian conduct, that is, between residues and derivations, sentiments and rationalizations. It is not simply one-to-one causation, but reciprocal causation, with influences running back and forth, springing forth a befuddling web of mutual interdependence. This makes it very difficult to determine precisely how much Christian doctrine actually influences conduct.
You might think this problem can be solved by comparing Christian behavior with, say, Islamic behavior. But this doesn’t work because all the other factors aren’t equal. Christians in the West are influenced by the secularization of the West, and are therefore a breed apart from Moslems, many of whom have not benefited at all from three hundred years of enlightened secularization in the West.
Now Rand and her orthodox followers make the mistake of assuming that Christian conduct follows Christian theory. That is one of the central themes of Leonard Peikoff’s “Religion Versus America.” Peikoff quotes several of the derivations made on behalf of religious sentiments and then makes the gratuitous assumption that religious conduct is merely a logical deduction from these derivations. Hence he quotes several incendiary statements about faith and then assumes religious people are going to derive all their conduct from beliefs gained “in the absence of evidence.” Now if this how religious people in fact determined their conduct in all aspects of life, they would long ago have disappeared from the earth. The fact that they are still around and flourishing suggests that their conduct is based on more substantial grounds.