Peirce's Triadic Logic

*We are indebted to the Department of Philosophy of Harvard University for permission to reproduce three pages from Peirce's Logic Notebook (1865-1909) and to quote from it and from other unpublished manuscripts. We cite them by the numbers assigned to them in the Catalogue which has been prepared by Professor Richard S. Robin. The Logic Notebook (Ms. 339) had been dismembered and its pages scattered, but it has recently been reassembled by Professor Don D. Roberts, and he hopes shortly to publish an account of it. Its pages were not numbered, but he has numbered the leaves in his arrangement of them. In his numbering, the pages we reproduce are 340 verso (Plate 1), 341 verso (Plate 2), and 344 recto (Plate 3).