Keywords: 4Fold Root Figure 3.jpg Figure 3 from The Fourfold Root of the Principle of Sufficient Reason by Arthur Schopenhauer Adobe snapshot from the scanned original book to be found at http //www archive org/details/onthefourfoldroo00schouoft Internet Archive org 1813 Creator Arthur Schopenhauer PD-old-100 On the Fourfold Root of the Principle of Sufficient Reason Triangle geometry |