Combining Philosophers

Ideas for Herodotus, Michal Walicki and Robert C. Stalnaker

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9 ideas

5. Theory of Logic / A. Overview of Logic / 1. Overview of Logic
To determine the patterns in logic, one must identify its 'building blocks' [Walicki]
     Full Idea: In order to construct precise and valid patterns of arguments one has to determine their 'building blocks'. One has to identify the basic terms, their kinds and means of combination.
     From: Michal Walicki (Introduction to Mathematical Logic [2012], History Intro)
     A reaction: A deceptively simple and important idea. All explanation requires patterns and levels, and it is the idea of building blocks which makes such things possible. It is right at the centre of our grasp of everything.
5. Theory of Logic / C. Ontology of Logic / 1. Ontology of Logic
Logical space is abstracted from the actual world [Stalnaker]
     Full Idea: Logical space is not given independently of the individuals that occupy it, but is abstracted from the world as we find it.
     From: Robert C. Stalnaker (Anti-essentialism [1979], p.85)
     A reaction: I very much like the second half of this idea, and am delighted to find Stalnaker endorsing it. I take the logical connectives to be descriptions of how things behave, at a high level of generality.
5. Theory of Logic / E. Structures of Logic / 1. Logical Form
We regiment to get semantic structure, for evaluating arguments, and understanding complexities [Stalnaker]
     Full Idea: The point of regimentation is to give a perspicuous representation of the semantic structure of an expression, making it easier to evaluate the validity of arguments and to interpret complex statements.
     From: Robert C. Stalnaker (Mere Possibilities [2012], 4.2)
     A reaction: This is an authoritative summary from an expert of why all philosophers must take an interest in logical form.
5. Theory of Logic / E. Structures of Logic / 2. Logical Connectives / e. or
In 'S was F or some other than S was F', the disjuncts need S, but the whole disjunction doesn't [Stalnaker]
     Full Idea: In 'either Socrates was a philosopher or someone other than Socrates was a philosopher', both propositions expressed by the disjuncts depend for their existence on the existence of Socrates, but the whole disjunction does not.
     From: Robert C. Stalnaker (Mere Possibilities [2012], 4.2)
     A reaction: Nice example, just the sort of thing we pay philosophers to come up with. He is claiming that propositions can exist in possible worlds in which the individuals mentioned do not exist.
5. Theory of Logic / F. Referring in Logic / 1. Naming / c. Names as referential
To understand a name (unlike a description) picking the thing out is sufficient? [Stalnaker]
     Full Idea: If we ask 'what must you know to understand a name?', the naïve answer is that one must know who or what it names - nothing more. (But no one would give this answer about what is needed to understand a definite description).
     From: Robert C. Stalnaker (Reference and Necessity [1997], 4)
     A reaction: Presumably this is naive because names can be full of meaning ('the Empress'), or description and reference together ('there's the man who robbed me') and so on. It's a nice starting point though. A number can serve as a name.
5. Theory of Logic / J. Model Theory in Logic / 1. Logical Models
A 'model' of a theory specifies interpreting a language in a domain to make all theorems true [Walicki]
     Full Idea: A specification of a domain of objects, and of the rules for interpreting the symbols of a logical language in this domain such that all the theorems of the logical theory are true is said to be a 'model' of the theory.
     From: Michal Walicki (Introduction to Mathematical Logic [2012], History E.1.3)
     A reaction: The basic ideas of this emerged 1915-30, but it needed Tarski's account of truth to really get it going.
5. Theory of Logic / J. Model Theory in Logic / 3. Löwenheim-Skolem Theorems
The L-S Theorem says no theory (even of reals) says more than a natural number theory [Walicki]
     Full Idea: The L-S Theorem is ...a shocking result, since it implies that any consistent formal theory of everything - even about biology, physics, sets or the real numbers - can just as well be understood as being about natural numbers. It says nothing more.
     From: Michal Walicki (Introduction to Mathematical Logic [2012], History E.2)
     A reaction: Illuminating. Particularly the point that no theory about the real numbers can say anything more than a theory about the natural numbers. So the natural numbers contain all the truths we can ever express? Eh?????
5. Theory of Logic / K. Features of Logics / 1. Axiomatisation
Axiomatic systems are purely syntactic, and do not presuppose any interpretation [Walicki]
     Full Idea: Axiomatic systems, their primitive terms and proofs, are purely syntactic, that is, do not presuppose any interpretation. ...[142] They never address the world directly, but address a possible semantic model which formally represents the world.
     From: Michal Walicki (Introduction to Mathematical Logic [2012], 4.1)
A compact axiomatisation makes it possible to understand a field as a whole [Walicki]
     Full Idea: Having such a compact [axiomatic] presentation of a complicated field [such as Euclid's], makes it possible to relate not only to particular theorems but also to the whole field as such.
     From: Michal Walicki (Introduction to Mathematical Logic [2012], 4.1)