Auke, I agree with you about the issues and priorities. AvB> Peirce is multi facetted. Each of us looks from a particular angle... I am not interested in what might be the final version Peirce wrote on the negation vs scroll issue... I can agree with you if we are discussing EG as a formal system. Yes. Formal EGs are the foundation. As Peirce himself said, logic as semiotic is much broader. It includes the methodeutic for analyzing and developing the immense variey empirical sciences. AvB> In a sense when we interpret we look at the input from all logical perspectives. Box-X running from 0000 to tttt, or from doubt to belief. Yes. All versions of classical first-order logic are sufficiently expressive to define all the patterns of mathematics. But the eg1911 version (as stated in L231) has a simplicity and symmetry that makes the definitions easier to state and the proofs easier to discover. For examples, see the slides I presented at an APA conference in 2015 and extended with more examples for another workshop: "Peirce, Polya, and Euclid: Integrating logic, heuristics, and geometry," http://jfsowa.com/talks/ppe.pdf . Note that the two-dimensional shaded areas of eg1911 can be generalized to 3-D shaded regions for proofs in solid geometry. They could even be generalized to 4-D regions for "stereoscopic moving images", which Peirce mentioned in L231. Those generalizations are not possible with the 1903 scrolls or the 1906 recto/verso sides of a 2-D sheet. Another important example is an unsolved research problem that was stated in 1988 and remained unsolved until 2010. Good logicians failed to find the proof because they made the same mistake that Peirce stated in 1893 (CP 4.76): "For [the reader] cannot reason at all without a monstrative sign of illation." See the proof with EG rules in slide 65 ff of ppe.pdf. Examples of signs of illation (or inference) include Peirce's claw symbol for if-then in Boolean algebra or his scroll in EGs. Those symbols are asymmetric, but the critical step for solving the problem of 1988 is easier to discover with the symmetric EG "permissions". As for the time and date when Peirce discovered the simplicity and generality of the eg1911 rules, compare R669, which ends abruptly shortly after 7:40 pm on 2 June 1911, to the completely rewritten R670, which begins on June 7. On June 22, he began L231, which contains a complete and polished version of the logic in R670. The date of the discovery is interesting for Peirce scholars. But the power and generality of eg1911 is demonstrated by the applications. For more examples, see "Diagrammatic reasoning with EGs and EGIF", http://jfsowa.com/pubs/diagrams.pdf ; "Reasoning with diagrams and images", http://www.collegepublications.co.uk/downloads/ifcolog00025.pdf John
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