### Ideas from 'Letters to Russell' by Gottlob Frege [1902], by Theme Structure

#### [found in 'From Frege to Gödel 1879-1931' (ed/tr Heijenoort,Jean van) [Harvard 1967,0-674-32449-8]].

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###### 6. Mathematics / A. Nature of Mathematics / 3. Nature of Numbers / g. Real numbers
 18253 I wish to go straight from cardinals to reals (as ratios), leaving out the rationals
 Full Idea: You need a double transition, from cardinal numbes (Anzahlen) to the rational numbers, and from the latter to the real numbers generally. I wish to go straight from the cardinal numbers to the real numbers as ratios of quantities. From: Gottlob Frege (Letters to Russell [1902], 1903.05.21), quoted by Michael Dummett - Frege philosophy of mathematics 21 'Frege's' A reaction: Note that Frege's real numbers are not quantities, but ratios of quantities. In this way the same real number can refer to lengths, masses, intensities etc.
###### 6. Mathematics / C. Sources of Mathematics / 6. Logicism / a. Early logicism
 18166 The loss of my Rule V seems to make foundations for arithmetic impossible
 Full Idea: With the loss of my Rule V, not only the foundations of arithmetic, but also the sole possible foundations of arithmetic, seem to vanish. From: Gottlob Frege (Letters to Russell [1902], 1902.06.22) A reaction: Obviously he was stressed, but did he really mean that there could be no foundation for arithmetic, suggesting that the subject might vanish into thin air?
###### 9. Objects / A. Existence of Objects / 2. Abstract Objects / c. Modern abstracta
 18269 Logical objects are extensions of concepts, or ranges of values of functions
 Full Idea: How are we to conceive of logical objects? My only answer is, we conceive of them as extensions of concepts or, more generally, as ranges of values of functions ...what other way is there? From: Gottlob Frege (Letters to Russell [1902], 1902.07.28), quoted by J. Alberto Coffa - The Semantic Tradition from Kant to Carnap 7 epigr A reaction: This is the clearest statement I have found of what Frege means by an 'object'. But an extension is a collection of things, so an object is a group treated as a unity, which is generally how we understand a 'set'. Hence Quine's ontology.