Combining Texts

All the ideas for 'Set Theory and related topics (2nd ed)', 'Laudatio: Prof Ruth Barcan Marcus' and 'Reasons for Actions and Desires'

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3 ideas

4. Formal Logic / D. Modal Logic ML / 7. Barcan Formula
If a property is possible, there is something which can have it [Williamson]
     Full Idea: Barcan's axiom says if there can be something that has a certain property, then there is something that can have that property. It and its converse are not obviously correct or incorrect. They claim that it is non-contingent what individuals there are.
     From: Timothy Williamson (Laudatio: Prof Ruth Barcan Marcus [2011], p.1)
     A reaction: Williamson defends the two Barcan formulas, but the more I understand them the less plausible they sound to me.
4. Formal Logic / F. Set Theory ST / 3. Types of Set / e. Equivalence classes
Equivalence relations are reflexive, symmetric and transitive, and classify similar objects [Lipschutz]
     Full Idea: A relation R on a non-empty set S is an equivalence relation if it is reflexive (for each member a, aRa), symmetric (if aRb, then bRa), and transitive (aRb and bRc, so aRc). It tries to classify objects that are in some way 'alike'.
     From: Seymour Lipschutz (Set Theory and related topics (2nd ed) [1998], 3.9)
     A reaction: So this is an attempt to formalise the common sense notion of seeing that two things have something in common. Presumably a 'way' of being alike is going to be a property or a part
20. Action / C. Motives for Action / 3. Acting on Reason / b. Intellectualism
I don't understand the idea of a reason for acting, but it is probably the agent's interests or desires [Foot]
     Full Idea: I am sure I do not understand the idea of a reason for acting, and I wonder whether anyone else does either. I incline to the view that all such reasons depend either on the agent's interests (meaning here what is in his interest) or else on his desires.
     From: Philippa Foot (Reasons for Actions and Desires [1972], p.156 Post)
     A reaction: It seems common to assume that a reason for an action must be something rational, but it makes sense to say that the reason for someone's action was an irrational whim. Is the reason for an action just the cause of the action?