Combining Texts

All the ideas for 'Letter Seven', 'On Second-Order Logic' and 'Scientific Attitude and Fallibilism'

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16 ideas

5. Theory of Logic / A. Overview of Logic / 7. Second-Order Logic
14249 Boolos reinterprets second-order logic as plural logic [Boolos, by Oliver/Smiley]
10830 Second-order logic metatheory is set-theoretic, and second-order validity has set-theoretic problems [Boolos]
5. Theory of Logic / C. Ontology of Logic / 1. Ontology of Logic
10829 A sentence can't be a truth of logic if it asserts the existence of certain sets [Boolos]
5. Theory of Logic / G. Quantification / 2. Domain of Quantification
10832 '∀x x=x' only means 'everything is identical to itself' if the range of 'everything' is fixed [Boolos]
5. Theory of Logic / K. Features of Logics / 4. Completeness
10834 Weak completeness: if it is valid, it is provable. Strong: it is provable from a set of sentences [Boolos]
5. Theory of Logic / K. Features of Logics / 6. Compactness
13841 Why should compactness be definitive of logic? [Boolos, by Hacking]
6. Mathematics / A. Nature of Mathematics / 4. Using Numbers / c. Counting procedure
14775 Numbers are just names devised for counting [Peirce]
6. Mathematics / B. Foundations for Mathematics / 4. Axioms for Number / e. Peano arithmetic 2nd-order
10833 Many concepts can only be expressed by second-order logic [Boolos]
6. Mathematics / C. Sources of Mathematics / 4. Mathematical Empiricism / c. Against mathematical empiricism
14776 That two two-eyed people must have four eyes is a statement about numbers, not a fact [Peirce]
11. Knowledge Aims / B. Certain Knowledge / 3. Fallibilism
14770 Reasoning is based on statistical induction, so it can't achieve certainty or precision [Peirce]
12. Knowledge Sources / A. A Priori Knowledge / 3. Innate Knowledge / a. Innate knowledge
14774 Innate truths are very uncertain and full of error, so they certainly have exceptions [Peirce]
12. Knowledge Sources / E. Direct Knowledge / 3. Inspiration
14773 A truth is hard for us to understand if it rests on nothing but inspiration [Peirce]
14772 If we decide an idea is inspired, we still can't be sure we have got the idea right [Peirce]
14771 Only reason can establish whether some deliverance of revelation really is inspired [Peirce]
15. Nature of Minds / C. Capacities of Minds / 2. Imagination
14769 Only imagination can connect phenomena together in a rational way [Peirce]
22. Metaethics / A. Ethics Foundations / 1. Nature of Ethics / a. Preconditions for ethics
168 To understand morality requires a soul [Plato]