Sam Harris begins The End of Faith sensibly, in view of his thesis that religious belief is dangerous, with an accounting of the crimes done in the name of faith, particularly those forms of faith that involve belief in the literalness of Scripture, and because of faith. He is primarily concerned with the People of the Book: Jews, Christians and Muslims. He argues forcefully that literal adherence to the canons of these religions leads necessarily to conflict and barbarism and that it is necessary, if humanity is to survive, to moderate attotudes toward the canons at a minimum or to abandon faith altogether. He rightly points out that such faith admits of no discourse, tolerance or compromise and that it is foolish to exempt faith claims from criticism.
He had me there, and I wish that he had gone no further. For he follows this line of reasoning with a gratuitous digression about moral equivalency that has nothing to do with the thesis of the book and which is nothing more than the assertion of normative propositions about terrorists versus soldiers that are no more justifiable by reason than the religious claims he has decried. That he cites the moral giant Alan Dershowitz should be enough information to permit you to assess the quality of the detour from the subject without my spending any time on it.
Then he concludes with the argument that there is no reason, in principle, that normative propositions cannot be treated just like all other truth claims and that it follows that we may yet have the benefit of scientific ethics. Harris argues that love may be shown by empirical evidence to promote happiness in the lover and the beloved and that it might form the basis of a morality predicated on reason. This somehow precedes a rather lengthy apology for torture and mass murder of recalcitrant religious folks, so I suppose that the author's concept of love differs radically from my own.
In any event, Harris seems to believe that he is the first person to have considered whether morality might be grounded on fact, that one might get to an "ought" from an "is". He certainly makes no mention of the treatment of the problem by others before him. Rather, he seems to assume that the discovery of relevant facts about the universe will necessarily inform a set of universally acceptable and justifiable normative consequences. Harris leaves the details of how this might be accomplished to greater minds.
Certainly, if science debunks factual assertions that underlie a religious belief, one might expect a reasonable person to abandon the religious belief. Perhaps this is Harris's hope. If so, I reckon it is a forlorn one given how tenaciously even civilized people cling to beliefs that stand in direct contradiction to any evidence that one might put before them.
I reckon that the book might have been far better if Harris had been content to argue that religious fundamentalism is a threat to survival and that we ought to be more outspoken in our criticism of it. He might have expounded on this at greater length and discussed how mechanisms that separate religious institutions from coercive political power can be maintained and strengthened. Also, he might have paid more attention to the way in which views about the canons in religions can be moderated. Harris seems to suggest that to be a Christian or a Muslim or a Jew requires (a) adherence to the literal truth and divine authorship of the canon, or (b) the decision to ignore inconvnenient parts of it. There are other alternatives that Harris might have explored. For example, one need not accept divine authorship or literal truth or the equal authority of every part of the canon. Moreover, in the path so many follow, one may simply choose to be a rather lukewarm practicioner. The choice is not fundamentalism or apostasy. And there are good reasons to examine what drives individuals into the fundamentalist camp.
Does belief inform and drive behavior as Harris claims? Perhaps in some cases. In religious matters, however, it is equally plausible that belief is summoned to rationalize behavior. Harris does not delve deeply enough into the premises. This could have been a useful book with a little editing and less superficial treatment of core concepts. It comes off more than anything else as a thinly veiled anti-Muslim diatribe. Muslims are the only religious category that he proposes for destruction. Harris calls for a war against Islam but not against Christianity or Judaism.