Combining Philosophers

All the ideas for Peter B. Lewis, Eric R. Scerri and Ian Rumfitt

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86 ideas

1. Philosophy / E. Nature of Metaphysics / 6. Metaphysics as Conceptual
Logic doesn't have a metaphysical basis, but nor can logic give rise to the metaphysics [Rumfitt]
3. Truth / A. Truth Problems / 1. Truth
The idea that there are unrecognised truths is basic to our concept of truth [Rumfitt]
3. Truth / B. Truthmakers / 7. Making Modal Truths
'True at a possibility' means necessarily true if what is said had obtained [Rumfitt]
4. Formal Logic / B. Propositional Logic PL / 1. Propositional Logic
Semantics for propositions: 1) validity preserves truth 2) non-contradition 3) bivalence 4) truth tables [Rumfitt]
4. Formal Logic / D. Modal Logic ML / 3. Modal Logic Systems / h. System S5
The logic of metaphysical necessity is S5 [Rumfitt]
'Absolute necessity' would have to rest on S5 [Rumfitt]
4. Formal Logic / E. Nonclassical Logics / 2. Intuitionist Logic
It is the second-order part of intuitionistic logic which actually negates some classical theorems [Rumfitt]
Intuitionists can accept Double Negation Elimination for decidable propositions [Rumfitt]
4. Formal Logic / F. Set Theory ST / 1. Set Theory
Most set theorists doubt bivalence for the Continuum Hypothesis, but still use classical logic [Rumfitt]
4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / a. Axioms for sets
The iterated conception of set requires continual increase in axiom strength [Rumfitt]
4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / b. Axiom of Extensionality I
A set may well not consist of its members; the empty set, for example, is a problem [Rumfitt]
A set can be determinate, because of its concept, and still have vague membership [Rumfitt]
4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / g. Axiom of Powers VI
If the totality of sets is not well-defined, there must be doubt about the Power Set Axiom [Rumfitt]
5. Theory of Logic / A. Overview of Logic / 1. Overview of Logic
Logic is higher-order laws which can expand the range of any sort of deduction [Rumfitt]
If a sound conclusion comes from two errors that cancel out, the path of the argument must matter [Rumfitt]
5. Theory of Logic / A. Overview of Logic / 3. Value of Logic
Logic guides thinking, but it isn't a substitute for it [Rumfitt]
5. Theory of Logic / A. Overview of Logic / 6. Classical Logic
Classical logic rules cannot be proved, but various lines of attack can be repelled [Rumfitt]
The case for classical logic rests on its rules, much more than on the Principle of Bivalence [Rumfitt]
If truth-tables specify the connectives, classical logic must rely on Bivalence [Rumfitt]
5. Theory of Logic / B. Logical Consequence / 1. Logical Consequence
Soundness in argument varies with context, and may be achieved very informally indeed [Rumfitt]
There is a modal element in consequence, in assessing reasoning from suppositions [Rumfitt]
We reject deductions by bad consequence, so logical consequence can't be deduction [Rumfitt]
Logical consequence is a relation that can extended into further statements [Rumfitt]
5. Theory of Logic / B. Logical Consequence / 3. Deductive Consequence |-
Normal deduction presupposes the Cut Law [Rumfitt]
5. Theory of Logic / D. Assumptions for Logic / 1. Bivalence
When faced with vague statements, Bivalence is not a compelling principle [Rumfitt]
5. Theory of Logic / D. Assumptions for Logic / 3. Contradiction
Contradictions include 'This is red and not coloured', as well as the formal 'B and not-B' [Rumfitt]
5. Theory of Logic / E. Structures of Logic / 2. Logical Connectives / a. Logical connectives
Standardly 'and' and 'but' are held to have the same sense by having the same truth table [Rumfitt]
In specifying a logical constant, use of that constant is quite unavoidable [Rumfitt]
The sense of a connective comes from primitively obvious rules of inference [Rumfitt]
5. Theory of Logic / H. Proof Systems / 2. Axiomatic Proof
Geometrical axioms in logic are nowadays replaced by inference rules (which imply the logical truths) [Rumfitt]
5. Theory of Logic / H. Proof Systems / 4. Natural Deduction
Introduction rules give deduction conditions, and Elimination says what can be deduced [Rumfitt]
5. Theory of Logic / I. Semantics of Logic / 3. Logical Truth
Logical truths are just the assumption-free by-products of logical rules [Rumfitt]
5. Theory of Logic / K. Features of Logics / 10. Monotonicity
Monotonicity means there is a guarantee, rather than mere inductive support [Rumfitt]
6. Mathematics / A. Nature of Mathematics / 3. Nature of Numbers / e. Ordinal numbers
Maybe an ordinal is a property of isomorphic well-ordered sets, and not itself a set [Rumfitt]
6. Mathematics / A. Nature of Mathematics / 4. Using Numbers / c. Counting procedure
A single object must not be counted twice, which needs knowledge of distinctness (negative identity) [Rumfitt]
6. Mathematics / A. Nature of Mathematics / 5. The Infinite / k. Infinitesimals
Infinitesimals do not stand in a determinate order relation to zero [Rumfitt]
6. Mathematics / B. Foundations for Mathematics / 1. Foundations for Mathematics
Cantor and Dedekind aimed to give analysis a foundation in set theory (rather than geometry) [Rumfitt]
6. Mathematics / B. Foundations for Mathematics / 5. Definitions of Number / c. Fregean numbers
Some 'how many?' answers are not predications of a concept, like 'how many gallons?' [Rumfitt]
9. Objects / B. Unity of Objects / 3. Unity Problems / e. Vague objects
Vague membership of sets is possible if the set is defined by its concept, not its members [Rumfitt]
An object that is not clearly red or orange can still be red-or-orange, which sweeps up problem cases [Rumfitt]
The extension of a colour is decided by a concept's place in a network of contraries [Rumfitt]
10. Modality / A. Necessity / 3. Types of Necessity
A distinctive type of necessity is found in logical consequence [Rumfitt, by Hale/Hoffmann,A]
10. Modality / A. Necessity / 5. Metaphysical Necessity
Metaphysical modalities respect the actual identities of things [Rumfitt]
10. Modality / A. Necessity / 6. Logical Necessity
Logical necessity is when 'necessarily A' implies 'not-A is contradictory' [Rumfitt]
A logically necessary statement need not be a priori, as it could be unknowable [Rumfitt]
Narrow non-modal logical necessity may be metaphysical, but real logical necessity is not [Rumfitt]
S5 is the logic of logical necessity [Rumfitt]
10. Modality / B. Possibility / 1. Possibility
Since possibilities are properties of the world, calling 'red' the determination of a determinable seems right [Rumfitt]
If two possibilities can't share a determiner, they are incompatible [Rumfitt]
10. Modality / E. Possible worlds / 1. Possible Worlds / e. Against possible worlds
If a world is a fully determinate way things could have been, can anyone consider such a thing? [Rumfitt]
Possibilities are like possible worlds, but not fully determinate or complete [Rumfitt]
11. Knowledge Aims / A. Knowledge / 2. Understanding
Medieval logicians said understanding A also involved understanding not-A [Rumfitt]
11. Knowledge Aims / C. Knowing Reality / 3. Idealism / d. Absolute idealism
Fichte, Schelling and Hegel rejected transcendental idealism [Lewis,PB]
Fichte, Hegel and Schelling developed versions of Absolute Idealism [Lewis,PB]
13. Knowledge Criteria / B. Internal Justification / 3. Evidentialism / a. Evidence
In English 'evidence' is a mass term, qualified by 'little' and 'more' [Rumfitt]
14. Science / A. Basis of Science / 4. Prediction
If a theory can be fudged, so can observations [Scerri]
14. Science / B. Scientific Theories / 4. Paradigm
The periodic system is the big counterexample to Kuhn's theory of revolutionary science [Scerri]
14. Science / D. Explanation / 1. Explanation / b. Aims of explanation
Scientists eventually seek underlying explanations for every pattern [Scerri]
14. Science / D. Explanation / 3. Best Explanation / a. Best explanation
The periodic table suggests accommodation to facts rates above prediction [Scerri]
19. Language / A. Nature of Meaning / 4. Meaning as Truth-Conditions
We understand conditionals, but disagree over their truth-conditions [Rumfitt]
19. Language / F. Communication / 3. Denial
The truth grounds for 'not A' are the possibilities incompatible with truth grounds for A [Rumfitt]
We learn 'not' along with affirmation, by learning to either affirm or deny a sentence [Rumfitt]
26. Natural Theory / B. Natural Kinds / 1. Natural Kinds
Natural kinds are what are differentiated by nature, and not just by us [Scerri]
If elements are natural kinds, might the groups of the periodic table also be natural kinds? [Scerri]
26. Natural Theory / D. Laws of Nature / 8. Scientific Essentialism / a. Scientific essentialism
The colour of gold is best explained by relativistic effects due to fast-moving inner-shell electrons [Scerri]
27. Natural Reality / B. Modern Physics / 4. Standard Model / a. Concept of matter
The stability of nuclei can be estimated through their binding energy [Scerri]
If all elements are multiples of one (of hydrogen), that suggests once again that matter is unified [Scerri]
27. Natural Reality / E. Chemistry / 1. Chemistry
A big chemistry idea is that covalent bonds are shared electrons, not transfer of electrons [Scerri]
Does radioactivity show that only physics can explain chemistry? [Scerri]
How can poisonous elements survive in the nutritious compound they compose? [Scerri]
Periodicity and bonding are the two big ideas in chemistry [Scerri]
Chemistry does not work from general principles, but by careful induction from large amounts of data [Scerri]
The electron is the main source of chemical properties [Scerri]
27. Natural Reality / E. Chemistry / 2. Modern Elements
It is now thought that all the elements have literally evolved from hydrogen [Scerri]
19th C views said elements survived abstractly in compounds, but also as 'material ingredients' [Scerri]
27. Natural Reality / E. Chemistry / 3. Periodic Table
Elements were ordered by equivalent weight; later by atomic weight; finally by atomic number [Scerri]
To explain the table, quantum mechanics still needs to explain order of shell filling [Scerri]
Orthodoxy says the periodic table is explained by quantum mechanics [Scerri]
Moseley showed the elements progress in units, and thereby clearly identified the gaps [Scerri]
Elements are placed in the table by the number of positive charges - the atomic number [Scerri]
Moseley, using X-rays, showed that atomic number ordered better than atomic weight [Scerri]
Some suggested basing the new periodic table on isotopes, not elements [Scerri]
Pauli explained the electron shells, but not the lengths of the periods in the table [Scerri]
Elements in the table are grouped by having the same number of outer-shell electrons [Scerri]
Since 99.96% of the universe is hydrogen and helium, the periodic table hardly matters [Scerri]
The best classification needs the deepest and most general principles of the atoms [Scerri]