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Single Idea 15252

[filed under theme 10. Modality / D. Knowledge of Modality / 4. Conceivable as Possible / b. Conceivable but impossible ]

Full Idea

Even in cases (such as Goldbach's Conjecture) which, if true, are logically necessary, we may be able to conceive the opposite. We can conceive of there being a number which is not the sum of two primes.

Gist of Idea

If Goldbach's Conjecture is true (and logically necessary), we may be able to conceive its opposite

Source

Harré,R./Madden,E.H. (Causal Powers [1975], 3.II)

Book Ref

Harré,R/Madden,E.H.: 'Causal Powers: A Theory of Natural Necessity' [Blackwell 1975], p.66


A Reaction

[attributed to Kneale] Ah, but can we conceive this (as Descartes would say) 'clearly and distinctly'? I can conceive circular squares, as long as I don't concentrate too hard.


The 10 ideas with the same theme [seems conceivable when not actually possible]:

Pythagoras' Theorem doesn't cease to be part of the essence of triangles just because we doubt it [Arnauld on Descartes]
We can imagine a point swelling and contracting - but not how this could be done [Hobbes]
Impossibilites are easily conceived in mathematics and geometry [Reid, by Molnar]
It is possible to conceive what is not possible [Shoemaker]
If Goldbach's Conjecture is true (and logically necessary), we may be able to conceive its opposite [Harré/Madden]
The impossible can be imagined as long as it is a bit vague [Lewis]
One can wrongly imagine two things being non-identical even though they are the same (morning/evening star) [Chalmers]
If claims of metaphysical necessity are based on conceivability, we should be cautious [Segal]
Conceivability may indicate possibility, but literary fantasy does not [Varzi]
Contradictory claims about a necessary god both seem apriori coherent [Schroeter]