Combining Texts

All the ideas for 'fragments/reports', 'First-Order Logic' and 'The Thought: a Logical Enquiry'

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23 ideas

2. Reason / A. Nature of Reason / 5. Objectivity
7740 There exists a realm, beyond objects and ideas, of non-spatio-temporal thoughts [Frege, by Weiner]
3. Truth / A. Truth Problems / 2. Defining Truth
19466 The word 'true' seems to be unique and indefinable [Frege]
3. Truth / C. Correspondence Truth / 3. Correspondence Truth critique
19465 There cannot be complete correspondence, because ideas and reality are quite different [Frege]
3. Truth / H. Deflationary Truth / 1. Redundant Truth
19468 The property of truth in 'It is true that I smell violets' adds nothing to 'I smell violets' [Frege]
5. Theory of Logic / A. Overview of Logic / 1. Overview of Logic
10282 Logic is the study of sound argument, or of certain artificial languages (or applying the latter to the former) [Hodges,W]
5. Theory of Logic / I. Semantics of Logic / 1. Semantics of Logic
10283 A formula needs an 'interpretation' of its constants, and a 'valuation' of its variables [Hodges,W]
10284 There are three different standard presentations of semantics [Hodges,W]
10285 I |= φ means that the formula φ is true in the interpretation I [Hodges,W]
5. Theory of Logic / J. Model Theory in Logic / 3. Löwenheim-Skolem Theorems
10288 Down Löwenheim-Skolem: if a countable language has a consistent theory, that has a countable model [Hodges,W]
10289 Up Löwenheim-Skolem: if infinite models, then arbitrarily large models [Hodges,W]
5. Theory of Logic / K. Features of Logics / 6. Compactness
10287 If a first-order theory entails a sentence, there is a finite subset of the theory which entails it [Hodges,W]
6. Mathematics / B. Foundations for Mathematics / 6. Mathematics as Set Theory / a. Mathematics is set theory
10286 A 'set' is a mathematically well-behaved class [Hodges,W]
7. Existence / A. Nature of Existence / 2. Types of Existence
19470 Thoughts in the 'third realm' cannot be sensed, and do not need an owner to exist [Frege]
7. Existence / D. Theories of Reality / 8. Facts / c. Facts and truths
19471 A fact is a thought that is true [Frege]
9. Objects / A. Existence of Objects / 3. Objects in Thought
9877 Late Frege saw his non-actual objective objects as exclusively thoughts and senses [Frege, by Dummett]
18. Thought / A. Modes of Thought / 1. Thought
19469 We grasp thoughts (thinking), decide they are true (judgement), and manifest the judgement (assertion) [Frege]
8162 Thoughts have their own realm of reality - 'sense' (as opposed to the realm of 'reference') [Frege, by Dummett]
9818 A thought is distinguished from other things by a capacity to be true or false [Frege, by Dummett]
18. Thought / A. Modes of Thought / 9. Indexical Thought
16379 Thoughts about myself are understood one way to me, and another when communicated [Frege]
19. Language / D. Propositions / 2. Abstract Propositions / a. Propositions as sense
19467 A 'thought' is something for which the question of truth can arise; thoughts are senses of sentences [Frege]
19. Language / D. Propositions / 5. Unity of Propositions
19472 A sentence is only a thought if it is complete, and has a time-specification [Frege]
26. Natural Theory / A. Speculations on Nature / 5. Infinite in Nature
1748 Archelaus was the first person to say that the universe is boundless [Archelaus, by Diog. Laertius]
27. Natural Reality / G. Biology / 3. Evolution
5989 Archelaus said life began in a primeval slime [Archelaus, by Schofield]