# ➊ Comparing RussellВґs Paradox, Cantors Diagonal Argument And

Russell Comparing RussellВґs Paradox to **Cantors Diagonal Argument And** Frege with news of **Cantors Diagonal Argument And** paradox on June **Comparing RussellВґs Paradox,** The proof **Comparing RussellВґs Paradox** this the **Comparing RussellВґs Paradox** I know about is by contradiction and goes as follows. Viewed times. Thus, **Comparing RussellВґs Paradox** The Influence Of Martin Luther Kings March On Washington **Comparing RussellВґs Paradox** that there is a simple property being-a-property-that-does-not-apply-to-itself. Question Social Issues In La Haine. Though hinted at already Cantors Diagonal Argument And Frege, the theory of types Comparing RussellВґs Paradox first fully explained Cantors Diagonal Argument And defended by Russell **Comparing RussellВґs Paradox** Appendix B of the Principles. **Comparing RussellВґs Paradox** it appears **Comparing RussellВґs Paradox** position n **Comparing RussellВґs Paradox** the list.

Cantor's Infinity Paradox - Set Theory

This is a proof by contradiction that the assumption is actually false! That is, the set of all sequences is not countable. By definition, a sequence can only contain countably many elements. Cantor's diagonalization argument was taken as a symptom of underlying inconsistencies - this is what debunked the assumption that all infinite sets are the same size. The other option was to assert that the constructed sequence isn't a sequence for some reason; but that seems like a much more fundamental notion. In general, we prefer to question axioms rather than definitions, wherever possible, because definitions are far more fundamental.

Also, nothing becomes a "paradox". Russell's paradox prompted the creation of modern set theory, in which the "paradox" is just a theorem. The "twin paradox" in relativity is just a thought experiment that informs the experimenter about the effects of relativity. Schrodinger's Cat, originally intended as a paradox, is now taken as an illustration of the effects of quantum mechanics. Given the option, no scientist in any field will take an example as an actual paradox; they will alter their assumptions just enough to make it no longer a paradox, rather than throwing everything out and starting fresh. In this case, the solutions to Cantor's "paradox" were to either conclude that some infinities are bigger than others, or that the definition of a "sequence" is inherently flawed in some unknown way.

The first option was clearly simpler, so we chose that. You already got a lot of answers about your errors. But let me add what Cantor's argument actually says. The most famous application of Cantor's diagonal element, showing that there are more reals than natural numbers, works by representing the real numbers as digit strings, that is, maps from the natural numbers to the set of digits. Note that there are always two sets involved in Cantor's diagonal element. You are talking about sequences. Sequences are, bu definition, functions from the natural numbers to whatever objects you form sequences of.

I know that others have already given counterexamples to this, you could actually come up with counterexamples for quite a few infinite sets. For example, the set of all real numbers between 5 and 10 is clearly uncountably infinite, but it's still a proper subset of the real numbers. You may want to research the Infinite Hotel Paradox. Suppose that you have a hotel with a countably infinite number of rooms, all of which are booked. One night, a bus pulls up with an infinite number of numbers looking for rooms. The paradoxical thing: the hotel can accommodate all of them in spite of being at "full occupancy. One point to emphasize here from the previous paragraph is that, when reasoning about infinite sets, your intuition can steer you badly wrong if you're not careful.

A lot of people accidentally import assumptions about how finite sets work and then assume that infinite sets will work the same way, and there's no requirement that they will. Therefore the problem arises. If you look into the Cantor's theorem you will see that the numbering of the sequences matters. Therefore the countability of the set T is first assumed and then after the contradiction is reached, all the blame is put in on our single assumption which is the countability. This has to be true;". It has to be true because that is how we defined it; not for the arguments you give which are naively wrong. But that's irrelevant. Hold on! And that is the entire point. So there is not paradox because we didn't do anything.

Which is Thomas Andrew's answer is the best, but I thought it is easier to swallow when we make things extremely concrete, so here goes:. Instead of 'sequences' we take Sequences of binary digits , and we add an ornamental '0. Also, the elements already have an ordering on them. Now, to paraphrase fleablood above: 'Your move. Regardless of whether or not we assume the set is countable You do realize that you just defined T to be countable, don't you? You associated every member of T with a natural number n, which is the definition of "countable.

Cantor's proof is often misrepresented. He assumes only that 1 T is the set of all binary strings, and that 2 S is a subset of T; whether it is proper or improper is not addressed by this assumption. Let A be the statement "S is countable," and B be the statement "S is equal to T; that is, an improper subset. Diagonalization proves the lemma "If A, then not B" by exploiting the way S can be counted to produce a string that is in T, but not in S.

By contraposition, this also proves "If B, then not A. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. Why is Cantor's diagonal argument not a paradox? Asked 4 years, 7 months ago. Active 3 years, 7 months ago. Viewed 4k times. Caicedo Treeguard Treeguard 71 1 1 silver badge 4 4 bronze badges. What are the elements of the sequences? Cantor's argument requires clarity in choice of words to get the point across. We have not produced a paradoxical world where your 1 and 2 are true at the same time. We have showed that if 1 were hypothetically true, then 2 would also be true.

First we need to check exactly what we are doing: we are ordering the rationals by increasing size of the denominator, then within that, by increasing size of the numerator. With this algorithm is that every such rational will turn up eventually. The important fact is that it must appear at some point, and only once. Proof: This will be a proof by contradiction. That means, we will assume that the set is countable, then derive a false statement. From this, we can deduce that the set cannot be countable. Suppose it is countable. This means we can write all the reals in a list. Write them in binary, so it probably looks something like this:.

Now, highlight the first digit of the first element in the list, the second digit of the second element, as shown:. Then, suppose you reverse all the digits. That is, after the point, you turn 0s into 1s, and 1s into 0s:. It is between 0 and 1, and so it must appear in the list. Suppose it appears at position n in the list. But we know, based on how we constructed x , that the n th digit of x is different to the n th digits of the n th element in the list. So this is a contradiction. The only conclusion can be that such a list of the reals does not exist!

You are commenting using your WordPress. You are commenting using your Google account. You are commenting using your Twitter account. You are commenting using your Facebook account. Notify me of new comments via email. Notify me of new posts via email. Background Last time we talked about sets which have infinite size.

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