We read excerpts from de Tocqueville's Democracy in America in my constitutional law class today (which is focusing on Church/State issues). De Tocqueville is an interesting case, and to me is a clear cut example of why making arguments based on "venerable old guy X believed it" is problematic.
To modern ears, de Tocqueville presents an interesting position. On the one hand, he extols the importance of religion in preserving America's democratic character. He thinks that religion serves several crucial and irreplaceable benefits to the state, and that it must be fostered--the private is public. Furthermore, he says that there is no major disagreement among the (Christian) religions in America on the important issues of religious outlook, and that this checks against strife, makes religion an important unifying force and prevents the ruinous religious warfare seen in Europe. On the other hand, he is equally vocal in giving credit to absolute church/state separation for causing this effect. Somewhat counter-intuitively, he holds that government involvement in religious affairs tends to have detrimental impacts on the positive aspects of religious experience.
So, liberals might use de Tocqueville to show why church/state separation is good. And conservatives might use him to point out that horrible things will happen if the general American belief in God is abandoned.
Two stock responses might immediately present themselves. First, de Tocqueville was far too sanguine about the level of religious unity in America at the time (even excluding non-Christian religious practices like Native American religions and animist religions brought over by African slaves--neither group probably was considered to be real people by de Tocqueville). Right around the time that he was happily writing about how great it was to be a Catholic in America, anti-Catholic bigotry really began to ramp up in the States (the Philadelphia Bible Riots, for example). So even if the consensus was true at the time he was writing (and I'm skeptical), it fractured very quickly. Second, one could simply note that whatever the level of religious pluralism in the 1840s, today we live in a highly diverse society. It is unclear how much his analysis applies to contemporary America, regardless of its aptness 160 years ago.
But even under his own terms, de Tocqueville is significantly more disturbing than we tend to portray him as. In class, I noted that de Tocqueville seemed to ignore the aforementioned anti-Catholic wave that was beginning to hit America at the time of his visit. My Professor responded that, to some extent, this might have been intentional--not because it was an inconvenient fact, but because it was actually encompassed in what de Tocqueville believed. De Tocqueville is quite explicit that the reason for religious consensus in America is because anyone who deviates from the orthodox position is simply afraid to speak up. And if they do assert an alternative position (e.g., atheism), American society will smite them down without blinking. Indeed, it is a bit unnerving how cheery he is at this prospect. If social (not governmental) pressure is de Tocqueville's favored method for ensuring religious unity, then a few friendly neighborhood acts of religious terrorism (to suppress potential fissures) may be exactly what is called for under his paradigm.
We tend to valorize people like de Tocqueville, so when they talk about how wonderful something is (like church/state separation, or religious unity), we think that their conclusion can simply be taken wholesale as a policy without dealing with the underlying analysis. We push under the rug the fact that the analysis might be based on false premises, or that the tactics might be of the sort modern Americans frown upon. But the problem is that his theories don't work without them. All the wonderful benefits that flow from unifying the public religious sphere only occur if we're willing to brutally suppress dissenters. If we're not willing to do that, then it's back to the drawing board.