Nussbaum on "The Rights of Conscience":
I just got Martha Nussbaum's book, Liberty of Conscience: In Defense of America's Tradition of Religious Equality. It looks to be a great read. And given her weight as a preeminent public intellectual, it's must reading for any serious student of the philosophy behind the religion clauses of America's Constitution.
From what I've read so far, I agree with her notion (something I've long trumpeted on the blogsphere) that equality-neutrality is the driver behind the Establishment Clause. This is important because in order for the Clause to properly incorporate and bind state and local governments (something which Justice Thomas and a few others have raised powerful reasons as to why it should not) it must relate to "rights," and equality is that right.
Yale law professor Akhil Amar made a similar point in his seminal book on the Bill of Rights, that even if the Establishment Clause doesn't properly incorporate, the Equal Protection Clause could still do much of what the Court currently has the Establishment Clause doing because it is equality rights that the Clause vindicates.
This notion of equal respect for citizens without regard to religious belief is paramount. Christian fundamentalists, Hindus and atheists all take their rights on an equal basis and are entitled to be viewed as equal citizens.
"Separation" in and of itself is not a "constitutional value" about which the religion clauses should be concerned. There may be some practical reasons as to why Church & State ought to be separated in particular circumstances -- avoiding entanglements, keeping religion pure from corrupt secular interests -- but it is always equal rights that should drive Establishment Clause inquiries, not "separation." Though the result may well be "separation." For instance, "under God" is not neutral and does not treat atheists or polytheists like equal citizens. Therefore, if this theory is taken thus far, under God should be taken out of the Pledge Of Allegiance because it does not treat its citizens equally along religious lines.
Princeton Provost Christopher Eisgruber and Dean of the University of Texas School of Law Lawrence Sager make a similar argument in their book Religious Freedom and the Constitution.
Finally, the University of Chicago Law blog features a lecture that Nussbaum recently gave on her thesis. Her research focuses extensively on Roger Williams (the man who coined the term "Separation of Church and State") as the originator of liberty and equality of conscience. It's amazing how such a fanatical orthodox Christian as Williams speaks to such a modern secular liberal as Nussbaum.
Nussbaum's book also answers Philip Hamburger's attempt to deconstruct the notion of Separation. Hamburger also explores Roger Williams as the originator of the phrase "separation of church and state" but tries to show how anathematic Williams' views were. And indeed, they were. When Williams first argued his case for secular government, theocracy was the prevailing norm in the American Colonies and the Puritan theocrats in Massachusetts banished Williams to found Rhode Island. Originators of world changing concepts (like secular government and religious liberty and equality) invariably start out as anathematic radicals.