The influence game, Mill/Humboldts/Thoreau edition

John Stuart Mill published On Liberty in 1859, having been working on it for five years; chapter III is his argument for individuality as a good in and of itself, as well as being useful to others: "In proportion to the development of his individuality, each person becomes more valuable to himself, and is therefore capable of being more valuable to others."

Mill's inspiration is proclaimed in his epigraph to the book:

The grand, leading principle, towards which every argument unfolded in these pages directly converges, is the absolute and essential importance of human development in its richest diversity.

That's Wilhelm von Humboldt, in The Sphere and Duties of Government (1852; tr. 1854). I wonder how many of those who today cherish "diversity" realize that the modern use of the term derives from a Prussian minister of education?

Another book published in 1854, though written over the preceding few years, contained a very similar sentiment to Humboldt's (and Mill's):

I would not have any one adopt my mode of living on any account; for, beside that before he has fairly learned it I may have found out another for myself, I desire that there may be as many different persons in the world as possible; but I would have each one be very careful to find out and pursue his own way, and not his father's or his mother's or his neighbor's instead.

Those words of Thoreau's have always been my favorite line from Walden. But is there any connection between Thoreau's idea and Humboldt's work?

I don't know whether Thoreau read Humboldt in the German, but another line of influence -- on both Thoreau and Humboldt -- is the latter's younger brother, the naturalist Alexander von Humboldt, whose botanical studies were a landmark in understanding the diversity of life as affected by its environment, and thus one of the early foundations of ecology. We know that Thoreau was reading Alexander von Humboldt at least by 1850, while writing Walden ....