This evening I finished reading Thoreau's first book, A Week on the Concord and Merrimack Rivers. Toward the very end, he writes as follows:
In summer we live out of doors, and have only impulses and feelings, which are all for action, and must wait commonly for the stillness and longer nights of autumn and winter before any thought will subside; we are sensible that behind the rustling leaves, and the stacks of grain, and the bare clusters of the grape, there is the field of a wholly new life, which no man has lived; that even this earth was made for more mysterious and nobler inhabitants than men and women. In the hues of October sunsets, we see the portals to other mansions than those which we occupy, not far off geographically.
[...]
The moon no longer reflects the day, but rises to her absolute rule, and the husbandman and hunter acknowledge her for their mistress. Asters and golden-rods reign along the way, and the life-everlasting withers not. The fields are reaped and shorn of their pride, but an inward verdure still crowns them. The thistle scatters its down on the pool, and yellow leaves clothe the vine, and naught disturbs the serious life of men. But behind the sheaves, and under the sod, there lurks a ripe fruit, which the reapers have not gathered, the true harvest of the year, which it bears forever, annually watering and maturing it, and man never severs the stalk which bears this palatable fruit.
I see a connection to a paragraph (previously quoted) from one of his Letters to Harrison Blake:
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, simultaneously naturalist and transcendentalist, always perceives the possibility of living a higher life, even partaking in moments of immortality ("the life everlasting"), as hinted in the same section of A Week:
Sometimes a mortal feels in himself Nature, not his Father but his Mother stirs within him, and he becomes immortal with her immortality. From time to time she claims kindredship with us, and some globule from her veins steals up into our own.
For Thoreau, such thoughts are often connected with autumn. His essay Autumnal Tints is fascinating and relevant here. He associates the fall of the year and the vibrant colors of a New England autumn with a ripening of existence, a certain mellowness and stronger flavor to life, "a late and perfect maturity", "an Indian-summer serenity", an appreciation of beauty separate from usefulness, the commencing of "a more independent and individual existence".
One of my favorite quotes from Walden is this:
There are nowadays professors of philosophy, but not philosophers. Yet it is admirable to profess because it was once admirable to live. To be a philosopher is not merely to have subtle thoughts, nor even to found a school, but so to love wisdom as to live according to its dictates, a life of simplicity, independence, magnanimity, and trust. It is to solve some of the problems of life, not only theoretically, but practically.
I'm starting to think of those four virtues as intimately associated with the four seasons.
As hinted in Autumnal Tints, in the time of one's late and perfect maturity one begins to lead a spiritually more "independent and individual existence"—to grow above and beyond the societal soil in which one was planted—to reflect upon one's experience and through that reflection to become more self-reliant. Thus fall is most closely associated in Thoreau's philosophy with independence.
Summer, by contrast, is a season in which we "are all for action"—a time of high flourishing, great-hearted ambition, riotous growth, fast progress, overflowing life—in a word, with magnanimity in its original sense of greatness of soul or enhanced liveliness.
As the foundation and precursor for such flourishing, spring is a time of being planted in the soil of one's family and society, of putting roots down into that soil, of gaining strength for one's greatest growth, of achieving solidity and structure in one's identity—of hope and trust in the future. Thoreau, ever mindful of etymology, could not have been unaware that trust, truth, and tree are cognate terms whose root meaning is strength, steadfastness, loyalty, constancy, solidity.
Of winter, Thoreau observed: "The wonderful purity of nature at this season is a most pleasing fact." (A Winter Walk.) "A cold and searching wind drives away all contagion, and nothing can withstand it but what has a virtue in it, and accordingly, whatever we meet with in cold and bleak places, as the tops of mountains, we respect for a sort of sturdy innocence, a Puritan toughness. All things beside seem to be called in for shelter, and what stays out must be part of the original frame of the universe, and of such valor as God himself. It is invigorating to breathe the cleansed air. Its greater fineness and purity are visible to the eye, and we would fain stay out long and late, that the gales may sigh through us, too, as through the leafless trees, and fit us for the winter,—as if we hoped so to borrow some pure and steadfast virtue, which will stead us in all seasons." Existence is stripped to its essentials, to its simplest elements.
Thus I'm beginning to feel my way along to a motif that might animate Walking With Thoreau: four seasonal walks to Thoreau's upland farm, where spring is about trust, summer about magnanimity, fall about independence, and winter about simplicity.
All this is subject to change, of course, as I read The Maine Woods, Walden, and his monumental Journals.