I've been reading Thoreau's letters to Harrison Blake, which are a veritable mine of philosophical insights. For the purposes of writing Walking With Thoreau, I'm especially interested so far in a fascinating vision he draws of cultivating the spiritual reaches of life (letter of May 28th, 1850):
Some absorbing employment on your higher ground,—your upland farm,—whither no cart-path leads, but where you mount alone with your hoe,—where the life everlasting grows; there you raise a crop which needs not to be brought down into the valley to a market; which you barter for heavenly products.
Thoreau returned to the same theme in his letter of July 21st, 1852:
All the world complain nowadays of a press of trivial duties and engagements, which prevents their employing themselves on some higher ground they know of; but, undoubtedly, if they were made of the right stuff to work on that higher ground, provided they were released from all those engagements, they would now at once fulfill the superior engagement, and neglect all the rest, as naturally as they breathe.
And again in his letter of February 27th, 1853:
The problem of life becomes, one cannot say by how many degrees, more complicated as our material wealth is increased,—whether that needle they tell of was a gateway or not,—since the problem is not merely nor mainly to get life for our bodies, but by this or a similar discipline to get life for our souls; by cultivating the lowland farm on right principles, that is, with this view, to turn it into an upland farm. You have so many more talents to account for. If I accomplish as much more in spiritual work as I am richer in worldly goods, then I am just as worthy, or worth just as much, as I was before, and no more. I see that, in my own case, money might be of great service to me, but probably it would not be; for the difficulty now is, that I do not improve my opportunities, and therefore I am not prepared to have my opportunities increased. Now, I warn you, if it be as you say, you have got to put on the pack of an upland farmer in good earnest the coming spring, the lowland farm being cared for; ay, you must be selecting your seeds forthwith, and doing what winter work you can; and, while others are raising potatoes and Baldwin apples for you, you must be raising apples of the Hesperides for them. (Only hear how he preaches!) No man can suspect that he is the proprietor of an upland farm,—upland in the sense that it will produce nobler crops, and better repay cultivation in the long run,—but he will be perfectly sure that he ought to cultivate it.
Perhaps I can structure Walking With Thoreau as a series of seasonal walks to Thoreau's upland farm? The idea is growing on me...