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Single Idea 14116

[filed under theme 6. Mathematics / B. Foundations for Mathematics / 5. Definitions of Number / b. Greek arithmetic ]

Full Idea

It used to be common to define numbers by means of 1, with 2 being 1+1 and so on. But this method was only applicable to finite numbers, made a tiresome different between 1 and the other numbers, and left + unexplained.

Gist of Idea

Numbers were once defined on the basis of 1, but neglected infinities and +

Source

Bertrand Russell (The Principles of Mathematics [1903], §109)

Book Ref

Russell,Bertrand: 'Principles of Mathematics' [Routledge 1992], p.112


A Reaction

Am I alone in hankering after the old approach? The idea of a 'unit' is what connected numbers to the patterns of the world. Russell's approach invites unneeded platonism. + is just 'and', and infinities are fictional extrapolations. Sounds fine to me.


The 10 ideas with the same theme [basic principles of arithmetic according to the early Greeks]:

Some quantities are discrete, like number, and others continuous, like lines, time and space [Aristotle]
The idea of 'one' is the foundation of number [Aristotle]
Each many is just ones, and is measured by the one [Aristotle]
Number is plurality measured by unity [Aristotle]
Euclid's common notions or axioms are what we must have if we are to learn anything at all [Euclid, by Roochnik]
A number is not a multitude, but a unified ratio between quantities [Newton]
Arithmetic is based on definitions, and Sums of equals are equal, and Differences of equals are equal [Mill]
Numbers were once defined on the basis of 1, but neglected infinities and + [Russell]
Mathematics originally concerned the continuous (geometry) and the discrete (arithmetic) [Shapiro]
Greek mathematics is wholly sensory, where ours is wholly inferential [Macbeth]