The great irony of those who advocated a modernist approach to history and morality is that they believed by discarding and thus transcending the particulars of doctrine and theological reflection, an unbiased and objective understanding of history and morality was possible. What this modernist understanding gave to the world instead was just one more biased view-- a view biased toward a closed universe, which meant that Christianity must be reinterpreted and wrestled away from the "superstitions" of "orthodox" Christianity. Since doctrine was simply emotive, theology was not useful for public discussions of morality, which left ethics in the hands of the politicians. Along with this came a bias against the church, which left authority in the hands of either the autonomous individual or the state; and a bias against Scripture, which left Enlightenment philosophers with arbitrary moral convictions that found their grounding in the notion of unalienable rights.
The point is that when the particular is rejected because it is seen as a polar opposite and a hindrance to the universal, one must find a justification for one's "universal" moral perspective that is not subjective. (Modernists would have saved themselves a lot of further trouble if they would have rejected the objective/subjective distinction as well.) That justification is the notion of unalienable rights, which transcend the particulars of time and place and culture. How do we know what unalienable rights are, and what is and is not a right? All reasonable people know. These truths are self-evident.
The twist of fate in all of this is that the general ethics of modernism, which was supposed to transcend the particulars of all religious convictions, sure looked Christian in many ways. It appears that Western thinkers were unable to transcend their context. In addition, modernist accounts of morality looked very Western European and Pre-Victorian, as well as sexist, racist, and anti-Semitic. It was hardly the kind of moral account anyone could embrace regardless of creed.
Moreover, such a general account of morality was so vague and watered down as to be quite unhelpful. Ben Franklin believed that the purpose of religious moral instruction was to produce kind and decent people who would be loyal to the state. The summation of such a moral narrative amounts to nothing more than, "Be nice to everybody." This is hardly the profound principle for which Jesus gave his life.
It is the truth of the matter that truth is intrinsic to the particulars of history. If love is important in the ministry of Jesus, it is only significant and authoritative in the context of a first-century Jew who was faithful to the Torah and who died and rose again. A general account of morality has failed to live up to expectations because the particulars of history, doctrine, and theology are too important to our identity to be discarded. One cannot have Christianity and discard the resurrection. One cannot have Judaism and reject Torah, one cannot have Islam and abandon the Qur'an. Particularities-- narratives-- are identity forming. If we discard them, we discard ourselves. The notions that all religions say basically the same thing is not only false, it can all too often be used in popular culture as an excuse to be intellectually lazy when it comes to understanding religion. It is also patronizing to the faithful adherents of all religions down through the centuries.
The notion of unalienable rights undercuts the indispensable significance of doctrine and the theology of the church, which are both necessary for moral reflection, personal and public; which is a false distinction in and of itself. All ethics are social ethics.