Orwell wrote:
ruveyn wrote:
I am a mathematician and I deal with infinities every working day. It is no big deal. I, with my finite brain capacity, can range the length and breadth of the infinite.
Only with cognitive tricks, of the same sort I use to play with infinity and visualize objects in four and five spatial dimensions. When you try to approach infinity honestly, laying your tricks, heuristics, and intuitions behind, you will quickly realize your limitations. The human mind is incapable of truly comprehending infinity. Indeed, there are a number of deeply counterintuitive results that crop up when you use infinities rigorously. Surely you are familiar with Abel and Cesaro summability, which lead you to truly bizarre results. And I'm certain you also know that the set of rationals and the set of integers have the same cardinality, despite the fact that the integers are a proper subset of the rationals. How does that make any sense? It appears to violate trichotomy.
Unless our axiom set is inconsistent, the only answer here is that we don't really understand infinity.
What is your point here? That the mathematical concept of "infinity", which to my mind
is relatively well understood, does not correspond to some other, philosophically more "correct" concept of infinity? That we can come up with all those nice counterintuitive results, about Cesaro summability, cardinalities of infinite sets, etc., implies, to my mind at least, just the opposite of what you posit, viz., I think that we have really gained a much more profound understanding of infinity, both in the "actual" and the "potential" sense, than our forefathers had in the 18th and 19th centuries.
Also, what do you mean with your remark about trichotomy? The axiom of trichotomy only applies to real numbers, not infinite quantities so I don't see its relevance here.
Lastly, that the cardinality of a proper subset of a set can equal that of the set itself is perfectly sensible. The concept of cardinality is often described as being a measure of how "infinite" a set is, but this is only a (bad) metaphor extrapolated from the finite case. In the finite case the cardinality indeed counts the number of elements in a set, but in the infinite case it simply doesn't do that anymore, because the operation of counting is meaningless for infinities. That two sets have equal cardinalities merely means that a bijection exists between the two.
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Dabey müssen wir nichts seyn, sondern alles werden wollen, und besonders nicht öffter stille stehen und ruhen, als die Nothdurfft eines müden Geistes und Körpers erfordert. - Goethe