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Ideas for 'Parmenides', 'Cardinality, Counting and Equinumerosity' and 'Reply to Professor Marcus'

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4 ideas

6. Mathematics / C. Sources of Mathematics / 1. Mathematical Platonism / a. For mathematical platonism
One is, so numbers exist, so endless numbers exist, and each one must partake of being [Plato]
     Full Idea: If one is, there must also necessarily be number - Necessarily - But if there is number, there would be many, and an unlimited multitude of beings. ..So if all partakes of being, each part of number would also partake of it.
     From: Plato (Parmenides [c.364 BCE], 144a)
     A reaction: This seems to commit to numbers having being, then to too many numbers, and hence to too much being - but without backing down and wondering whether numbers had being after all. Aristotle disagreed.
6. Mathematics / C. Sources of Mathematics / 1. Mathematical Platonism / b. Against mathematical platonism
Children can use numbers, without a concept of them as countable objects [Heck]
     Full Idea: For a long time my daughter had no understanding of the question of how many numerals or numbers there are between 'one' and 'five'. I think she lacked the concept of numerals as objects which can themselves be counted.
     From: Richard G. Heck (Cardinality, Counting and Equinumerosity [2000], 5)
     A reaction: I can't make any sense of numbers actually being objects, though clearly treating all sorts of things as objects helps thinking (as in 'the victory is all that matters').
6. Mathematics / C. Sources of Mathematics / 6. Logicism / d. Logicism critique
Equinumerosity is not the same concept as one-one correspondence [Heck]
     Full Idea: Equinumerosity is not the same concept as being in one-one correspondence with.
     From: Richard G. Heck (Cardinality, Counting and Equinumerosity [2000], 6)
     A reaction: He says this is the case, even if they are coextensive, like renate and cordate. You can see that five loaves are equinumerous with five fishes, without doing a one-one matchup.
We can understand cardinality without the idea of one-one correspondence [Heck]
     Full Idea: One can have a perfectly serviceable concept of cardinality without so much as having the concept of one-one correspondence.
     From: Richard G. Heck (Cardinality, Counting and Equinumerosity [2000], 3)
     A reaction: This is the culmination of a lengthy discussion. It includes citations about the psychology of children's counting. Cardinality needs one group of things, and 1-1 needs two groups.