Faith is the greatest falling of mankind.

The definition of "faith" offered is not very clear. I don't want to debate semantics, but I assume you mean religious faith involving religious teachings passed from one believer to another as articles of faith without derivation by logic from provable facts. I will stipulate that there is no god or gods, so that articles of religious faith are not derived by revelation or from any supernatural source. The question is solely whether "[Religious] faith is the greatest falling [failing] of mankind." The origin of religion is the natural instinct in mankind to understand his environment. He does that by forming theories and seeing how well they work. This is not a quick and decisive process. Postulating a volcano god that wants sacrifices seems to work due to the confirmation fallacy. Most times the sacrifice is made, the volcano does not erupt. When the volcano does erupt, the conclusion is that for some reason to be divined by a priest the god was not satisfied. whatever else is done is likely to be confirmed by the volcano not erupting. Thus religion is derived from a natural desire to understand how nature works. As science provides alternative explanations, the domain of religion natural shrinks to questions that science has not explained. Religion not only attempts to explain what works in nature, but what works in society. Thus Christians once thought that the Bible condoned slavery, but now Christians are sure that their religion prohibits slavery. The major religions have evolved substantially. In support of this claim of religious social evolution note that most of the aborrent religions have disappeared; human sacifice is distinctly out of favor. Moreover, the oldest of the major religions, Buddhism, is the least violent and the newest, Islam, is the most violent and least progressive. Christianity is somewhere in between. It is quite true that a great deal of bad behavior can be attributed to religion, but supposing that religion has not evolved fails to recognize a central fact about religion as a social force. Pro cites The Crusades, which probably a poor example, as there were as many political factors involved as religious. However, there are many good examples, such as witch trials and the Inquisition. However, Pro cites the Holocaust, which is a major misunderstanding. The Holocaust was a product of Fascism, not a product of religion. The modern alternatives to religion are "isms." Fascism, Communism, and many lesser political offshoots. What isms offer is simple explanations to things in society for which simple explanations. Thus fascism explained problems in the German society of the time, racism explains problems, heavy-duty political ideologies explain problems in modern society. Modern ideologies cast non-believers in the ideology in just the same role as religious true believers cast heretics. However, a couple thousand years of social evolution have tempered the bulk of religion, but political ideologies are fresh and untempered. Note that modern ideologies also cater to the instinct for tribalism, to be part of a group and to feel special by being part of the group. That is part of the force behind religion. It is not necessarily harmful. Sports fans form associations that cannot be rationally derived, but except for occasional mental cases, the fervent associations are harmless. If religion is not the greatest failing of mankind, then something else must be. I claim the greatest failing of mankind is the innate need to accept simple explanations of complex problems. I think this is natural and innate. If humans had to develop complex theories based upon testing scientific hypotheses, they would be quickly eaten by creatures who were not so contemplative. Making quick simple theories is a survival advantage in the primitive world where mankind evolved. It leads to great problems in a complex society. Taking things on faith is not exactly the same as accepting things without reason. Parents tell children not to touch a hot stove, and they hope the child will comply based upon the authority of the parents. The child learns to do so, even lacking knowledge studies of heat transfer properties and the effects of excessive heat on human tissue. The acceptance is on the basis of parental authority; the child benefits from the advice. Similarly, religion teaches the rules for a good society. These are accepted, I claim, based more on the authority of tradition then the authority of God. We know this because the is a religion to provide divine authority for virtually anything. Over time, most of the rules have become reasonable. The Golden Rule has merit, no matter how derived. the wild and crazy stuff by and large has no consequence in social behavior. Just as professional chefs learn how to properly touch a hot stove, mature religious people work towards a form of religion with which they are comfortable. Lord knows there are no limits to the variations. I repeat that I fully agree that religion produces Jihadists and such. However, the long evolution of the major religions minimizes those aberrations. I would be far more comfortable living in a society dominated by Buddhism then in one dominated by a modern all-explaining ideology like fascism or communism. The flaw in mankind lies at a higher level than religion, and what tempers the flaw is evolving tradition.