In Human, All Too Human (Book II, Part 1, Section 408), Nietzsche wrote:
I, too, have been in the underworld, like Odysseus, and will often be there again; and I have not only sacrificed rams to be able to talk with the dead, but have not spared my own blood as well. There have been four pairs who did not refuse themselves to me, the sacrificer: Epicurus and Montaigne, Goethe and Spinoza, Plato and Rousseau, Pascal and Schopenhauer. With these I have had to come to terms when I have wandered long alone, from them will I accept judgment, to them will I listen when in doing so they judge one another. Whatever I say, resolve, cogitate for myself and others: upon these eight I fix my eyes and see theirs fixed upon me. -- May the living forgive me if they sometimes appear to me as shades, so pale and ill-humoured, so restless and, alas, so lusting for life: whereas those others then seem to me so alive, as though now, after death, they could never again grow weary of life. Eternal liveliness, however, is what counts: what does "eternal life", or life at all, matter to us!
I, too, feel that there are such "pairs" in my mental life. One pair consists of Nietzsche and Epicurus (who gave such opposite answers to the question of the purpose of living); another consists of Aristotle and Thoreau; and there are perhaps other pairs as well (Whitman and Rand? Maslow and Bronowski? Emerson and Zamyatin?).
The opposition of Aristotle and Thoreau is strongest in the political or social realm (though it is felt also in the search for knowledge, where Thoreau seeks always to get his hands dirty through direct observation of discrete phenomena, whereas Aristotle was a master of logic, abstraction, and systematization). Aristotle wrote (Politics, Book 1, Chapter 2, 1252b27-1253a4):
When several villages are united in a single complete community, large enough to be nearly or quite self-sufficing, a commonwealth comes into existence, originating in the bare needs of life, and continuing in existence for the sake of a good life. And therefore, if the earlier forms of society are natural, so is the commonwealth, for it is the end or goal of them, and the nature of a thing is its end or goal. For what each thing is when fully developed, we call its nature, whether we are speaking of a man, a horse, or a family. Besides, the final cause and end of a thing is the best, and to be self-sufficing is the end and the best. Hence it is evident that the commonwealth is a creation of nature, and that man is by nature a social animal. And he who by nature and not by mere accident is outside a commonwealth, is either a bad man or above humanity...
Thoreau, by contrast, felt few if any ties to his fellow man. Here is a characteristic passage from his journals (July 26, 1852):
By my intimacy with nature I find myself withdrawn from man. My interest in the sun and the moon, in the morning and the evening, compels me to solitude.
The grandest picture in the world is the sunset sky. In your higher moods what man is there to meet? You are of necessity isolated. The mind that perceives clearly any natural beauty is in that instant withdrawn from human society. My desire for society is infinitely increased; my fitness for any actual society is diminished.
The tension between sociality and solitude, between Aristotle and Thoreau if you will, finds expression in the modern libertarian movement. I've observed it most recently in the wrangling within the Free State Project over which state the FSPers will choose to move to. This conflict is often perceived as one of East (New Hampshire or Delaware) vs. West (Montana or Wyoming), or of Eastern city people vs. Western rural folk. But that is the mere surface of things. I think the fundamental disagreement is over the degree of one's involvement in society. The Thoreauvians seem compelled to solitude: they believe deeply in self-sufficiency, a belief which at its most extreme manifests itself as a desire to return to the land, work for oneself even if that means a lower standard of living, hunt and fish and grow one's own food, unplug from the power grid, homeschool one's children, abstain from political activities, and in general withdraw from human society as much as possible. The Aristotelians find human society perfectly natural: they eagerly work within the political process, take advantage of the division of labor, are employed by organizations, accept certain rules as a cost of social interaction, are comfortable in towns and cities, and highly value both economic freedom and material prosperity. Naturally, these are tendencies, not hard-and-fast categories; exceptions and admixtures abound. But I do think they capture many of the tensions within the libertarian community, and within individual libertarians.
For the record, I'm probably more of an Aristotelian than a Thoreauvian.