For an interesting treatment of the issue, see "The Way of Torah" by Rav
Nahum Rabinovitch in The Edah Journal [now Me'orot] 3:1, available on line
at [
www.edah.org]
Rav Rabinovitch takes the view that "the Torah's method is to be a
catalyst for the evolution of moral values in history, i.e. from polygamy
to monogamy, from slavery to freedom, from war to peace, and from coercion
to liberty. Some Torah laws are given in accordance with minimal
standards, some for study alone, and some for realization of moral and
spiritual ideals" (quoted from the article's abstract). His article
provides detailed analyses of several examples of the process.
Joel Linsider