The longest silence is the most pertinent question
most pertinently put. Emphatically silent.
The most important question, whose answers concern
us more than any, are never put in any other way.
~ Henry David Thoreau, January 4, 1851, Journal Entry*
Henry David Thoreau at American Transcendentalism Web
Profile in Stanford Encyclopedia of Philosophy
The Thoreau Reader
The Thoreau Society
Friends of Walden Pond
Life With Principle: Thoreau's Voice in Our Time
* The Journal of Henry D. Thoreau in Fourteen Volumes Bound as Two, Volumes I-VII, 1837 - October, 1855 on GoogleBooks
A Year in Thoreau's Journal 1851 on GoogleBooks