Hardcover. Condition: Very Good. 1872 reissue of 1855 original. Front joint weakening, stain on top corner, ink name and date on front endpaper. xii, 228 pp., 16-page publisher's ad follows text. German text. Author's magnum opus, advocating scientific materialism and attempting to prove the indestructibility of matter and force. Foundational to the freethinkers' movement in Germany.