Ideas of C.I. Lewis, by Theme

[American, 1883 - 1964, Born at Stoneham. Professor at Harvard University.]

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4. Formal Logic / D. Modal Logic ML / 3. Modal Logic Systems / h. System S5
The simplest of the logics based on possible worlds is Lewis's S5 [Girle]
5. Theory of Logic / A. Overview of Logic / 1. Overview of Logic
There are several logics, none of which will ever derive falsehoods from truth
5. Theory of Logic / D. Assumptions for Logic / 2. Excluded Middle
Excluded middle is just our preference for a simplified dichotomy in experience
5. Theory of Logic / F. Referring in Logic / 1. Naming / a. Names
Names represent a uniformity in experience, or they name nothing
10. Modality / A. Necessity / 2. Nature of Necessity
Equating necessity with informal provability is the S4 conception of necessity [Read]
10. Modality / A. Necessity / 11. Denial of Necessity
Necessary truths are those we will maintain no matter what
10. Modality / B. Possibility / 8. Conditionals / a. Conditionals
Modal logic began with translation difficulties for 'If...then' [Girle]
12. Knowledge Sources / A. A Priori Knowledge / 7. A Priori from Convention
We can maintain a priori principles come what may, but we can also change them
13. Knowledge Criteria / B. Internal Justification / 4. Foundationalism / a. Foundationalism
If anything is to be probable, then something must be certain
18. Thought / C. Content / 8. Intension
Extension is the class of things, intension is the correct definition of the thing, and intension determines extension
18. Thought / E. Abstraction / 2. Abstracta by Selection
We have to separate the mathematical from physical phenomena by abstraction
26. Natural Theory / D. Laws of Nature / 8. Scientific Essentialism / a. Scientific essentialism
Science seeks classification which will discover laws, essences, and predictions