Combining Philosophers

All the ideas for Xenophanes, Feferman / Feferman and William Whewell

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19 ideas

4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / j. Axiom of Choice IX
The Axiom of Choice is consistent with the other axioms of set theory [Feferman/Feferman]
Axiom of Choice: a set exists which chooses just one element each of any set of sets [Feferman/Feferman]
Platonist will accept the Axiom of Choice, but others want criteria of selection or definition [Feferman/Feferman]
The Trichotomy Principle is equivalent to the Axiom of Choice [Feferman/Feferman]
Cantor's theories needed the Axiom of Choice, but it has led to great controversy [Feferman/Feferman]
5. Theory of Logic / J. Model Theory in Logic / 1. Logical Models
A structure is a 'model' when the axioms are true. So which of the structures are models? [Feferman/Feferman]
Tarski and Vaught established the equivalence relations between first-order structures [Feferman/Feferman]
5. Theory of Logic / J. Model Theory in Logic / 3. Löwenheim-Skolem Theorems
Löwenheim-Skolem says if the sentences are countable, so is the model [Feferman/Feferman]
Löwenheim-Skolem Theorem, and Gödel's completeness of first-order logic, the earliest model theory [Feferman/Feferman]
5. Theory of Logic / K. Features of Logics / 4. Completeness
If a sentence holds in every model of a theory, then it is logically derivable from the theory [Feferman/Feferman]
5. Theory of Logic / K. Features of Logics / 7. Decidability
'Recursion theory' concerns what can be solved by computing machines [Feferman/Feferman]
Both Principia Mathematica and Peano Arithmetic are undecidable [Feferman/Feferman]
13. Knowledge Criteria / D. Scepticism / 1. Scepticism
If we succeed in speaking the truth, we cannot know we have done it [Xenophanes]
13. Knowledge Criteria / E. Relativism / 1. Relativism
If God had not created honey, men would say figs are sweeter [Xenophanes]
14. Science / D. Explanation / 2. Types of Explanation / d. Consilience
Consilience is a common groundwork of explanation [Whewell]
26. Natural Theory / A. Speculations on Nature / 6. Early Matter Theories / e. The One
The basic Eleatic belief was that all things are one [Xenophanes, by Plato]
28. God / A. Divine Nature / 2. Divine Nature
Xenophanes said the essence of God was spherical and utterly inhuman [Xenophanes, by Diog. Laertius]
28. God / C. Attitudes to God / 5. Atheism
Ethiopian gods have black hair, and Thracian gods have red hair [Xenophanes]
Mortals believe gods are born, and have voices and clothes just like mortals [Xenophanes]