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Ideas for 'Structures and Structuralism in Phil of Maths', 'When Does a Life Begin?' and 'My Philosophical Development'

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3 ideas

5. Theory of Logic / E. Structures of Logic / 1. Logical Form
Leibniz bases everything on subject/predicate and substance/property propositions [Russell]
     Full Idea: The metaphysics of Leibniz was explicitly based upon the doctrine that every proposition attributes a predicate to a subject and (what seemed to him almost the same thing) that every fact consists of a substance having a property.
     From: Bertrand Russell (My Philosophical Development [1959], Ch.5)
     A reaction: I think it is realised now that although predicates tend to attribute properties to things, they are far from being the same thing. See Idea 4587, for example. Russell gives us an interesting foot in the door of Leibniz's complex system.
5. Theory of Logic / F. Referring in Logic / 1. Naming / e. Empty names
Names are meaningless unless there is an object which they designate [Russell]
     Full Idea: Unlike descriptions, names are meaningless unless there is an object which they designate.
     From: Bertrand Russell (My Philosophical Development [1959], Ch.14)
     A reaction: This interests Russell because of its ontological implications. If we reduce language to names, we can have a pure ontology of 'objects'. We need a system for saying whether a description names something - which is his theory of definite descriptions.
5. Theory of Logic / G. Quantification / 5. Second-Order Quantification
Three types of variable in second-order logic, for objects, functions, and predicates/sets [Reck/Price]
     Full Idea: In second-order logic there are three kinds of variables, for objects, for functions, and for predicates or sets.
     From: E Reck / M Price (Structures and Structuralism in Phil of Maths [2000], §5)
     A reaction: It is interesting that a predicate seems to be the same as a set, which begs rather a lot of questions. For those who dislike second-order logic, there seems nothing instrinsically wicked in having variables ranging over innumerable multi-order types.