I wouldn't interpret Adams as saying that the humanities have no value until after the war is over and the nation established—I think he's saying that he doesn't have as much time to focus on them as he would like to have, and he hopes that future generations will have that time.

At the beginning of the letter he says this:

> Since my Arrival this time I have driven about Paris, more than I did before. The rural Scenes around this Town are charming. The public Walks, Gardens, &c. are extreamly beautifull. The Gardens of the Palais Royal, the Gardens of the Tuilleries, are very fine. The Place de Louis 15, the Place Vendome or Place de Louis 14, the Place victoire, the Place royal, are fine Squares, ornamented with very magnificent statues. I wish I had time to describe these objects to you in a manner, that I should have done, 25 Years ago, but my Head is too full of Schemes and my Heart of Anxiety to use Expressions borrowed from you know whom.

Note that he does say he took time to view and appreciate the things he found in Paris—what he laments is that he does not have the mental focus to study and describe them in detail to his wife.