Language Log is usually a fun read; the post there on Thanks Giving is no exception, and also has a nice quote from Thomas Jefferson on Presidental “declarations” with respect to matters religious. Apparently, in 1808, when Jefferson was asked to “to proclaim a national thanksgiving day devoted to fasting (?) and prayer”, he responded with the kind of wisdom we can only dream of from a contemporary president:

I consider the government of the U S. as interdicted by the Constitution from intermeddling with religious institutions, their doctrines, discipline, or exercises. … But it is only proposed that I should recommend, not prescribe a day of fasting & prayer. That is, that I should indirectly assume to the U.S. an authority over religious exercises which the Constitution has directly precluded them from. It must be meant too that this recommendation is to carry some authority, and to be sanctioned by some penalty on those who disregard it; not indeed of fine and imprisonment, but of some degree of proscription perhaps in public opinion. And does the change in the nature of the penalty make the recommendation the less a law of conduct for those to whom it is directed? I do not believe it is for the interest of religion to invite the civil magistrate to direct its exercises, its discipline, or its doctrines; nor of the religious societies that the general government should be invested with the power of effecting any uniformity of time or matter among them. Fasting & prayer are religious exercises. The enjoining them an act of discipline. Every religious society has a right to determine for itself the times for these exercises, & the objects proper for them, according to their own particular tenets; and this right can never be safer than in their own hands, where the constitution has deposited it.

Why can’t we have one of those again?