Combining Philosophers

Ideas for Herodotus, Jonathan Schaffer and Hugh MacColl

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2 ideas

4. Formal Logic / D. Modal Logic ML / 3. Modal Logic Systems / d. System T

14607	T adds □p→p for reflexivity, and is ideal for modeling lawhood [Schaffer,J]
	Full Idea: System T is a normal modal system augmented with the reflexivity-generating axiom □p→p, and is, I think, the best modal logic for modeling lawhood.
	From: Jonathan Schaffer (Causation and Laws of Nature [2008], n46)
	A reaction: Schaffer shows in the article why transitivity would not be appropriate for lawhood.

4. Formal Logic / F. Set Theory ST / 3. Types of Set / b. Empty (Null) Set

21548	The null class is the class with all the non-existents as its members [MacColl, by Lackey]
	Full Idea: In 1905 the Scottish logician Hugh MacColl published a paper in which he argued that the null class in logic should be taken as the class with all the non-existents as its members.
	From: report of Hugh MacColl (Symbolic Reasoning [1905]) by Douglas Lackey - Intros to Russell's 'Essays in Analysis' p.95
	A reaction: For the null object (zero) Frege just chose one sample concept with an empty extension. MacColl's set seems to have a lot of members, given that it is 'null'. How many, I wonder? Russell responded to this paper.