Cantors diagonal

An octagon has 20 diagonals. A shape’s diagonals are determined by counting its number of sides, subtracting three and multiplying that number by the original number of sides. This number is then divided by two to equal the number of diagon...

Cantors diagonal. $\begingroup$ cantors diagonal argument $\endgroup$ - JJR. May 22, 2017 at 12:59. 4 $\begingroup$ The union of countably many countable sets is countable. $\endgroup$ - Hagen von Eitzen. May 22, 2017 at 13:10. 3 $\begingroup$ What is the base theory where the argument takes place?

Cantor's diagonal argument is a paradox if you believe** that all infinite sets have the same cardinality, or at least if you believe** that an infinite set and its power set have the same cardinality. Cantor's diagonal argument is not a paradox if you use it to conclude that a set's cardinality is not that of its power set.

Cantor's proof shows directly that ℝ is not only countable. That is, starting with no assumptions about an arbitrary countable set X = {x (1), x (2), x (3), …}, you can find a number y ∈ ℝ \ X (using the diagonal argument) so X ⊊ ℝ. The reasoning you've proposed in the other direction is not even a little bit similar.ÐÏ à¡± á> þÿ C E ...Ok so I know that obviously the Integers are countably infinite and we can use Cantor's diagonalization argument to prove the real numbers are uncountably infinite...but it seems like that same argument should be able to be applied to integers?. Like, if you make a list of every integer and then go diagonally down changing one digit at a time, you should get a new integer which is guaranteed ...I recently found Cantor's diagonal argument in Wikipedia, which is a really neat proof that some infinities are bigger than others (mind blown!). But then I realized this leads to an apparent paradox about Cantor's argument which I can't solve. Basically, Cantor proves that a set of infinite binary sequences is uncountable, right?.$\begingroup$ Notice that even the set of all functions from $\mathbb{N}$ to $\{0, 1\}$ is uncountable, which can be easily proved by adopting Cantor's diagonal argument. Of course, this argument can be directly applied to the set of all function $\mathbb{N} \to \mathbb{N}$. $\endgroup$This article discusses two theorems of Georg Cantor: Cantor's Little Theorem and Cantor's Diagonal Theorem. The results are obtained by generalizing the method of proof of the well known Cantor's theorem about the cardinalities of a set and its power set. As an application of these, Gödel's first incompleteness theorem is proved. Hints are given as to how to derive other deeper ...Screenshot (by author) from openai.com. The GPT-4 Technical Report contains many other simulated exams used to test the reasoning and problem solving ability of GPT-4. When it comes to Mathematics, GPT-4 ranked in the top 11% of scores on the SAT Math Test (a significant improvement from GPT-3.5).About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new features NFL Sunday Ticket Press Copyright ...

Cantor's proof is not saying that there exists some flawed architecture for mapping $\mathbb N$ to $\mathbb R$. Your example of a mapping is precisely that - some flawed (not bijective) mapping from $\mathbb N$ to $\mathbb N$. What the proof is saying is that every architecture for mapping $\mathbb N$ to $\mathbb R$ is flawed, and it also gives you a set of instructions on how, if you are ...Yes, because Cantor's diagonal argument is a proof of non existence. To prove that something doesn't, or can't, exist, you have two options: Check every possible thing that could be it, and show that none of them are, Assume that the thing does exist, and show that this leads to a contradiction of the original assertion.I have found that Cantor's diagonalization argument doesn't sit well with some people. It feels like sleight of hand, some kind of trick. Let me try to outline some of the ways it could be a trick. You can't list all integers One argument against Cantor is that you can never finish writing z because you can never list all of the integers ...It is argued that the diagonal argument of the number theorist Cantor can be used to elucidate issues that arose in the socialist calculation debate of the 1930s and buttresses the claims of the Austrian economists regarding the impossibility of rational planning. 9. PDF. View 2 excerpts, cites background.Posted by u/1stte - 1 vote and 148 commentsYes, because Cantor's diagonal argument is a proof of non existence. To prove that something doesn't, or can't, exist, you have two options: Check every possible thing that could be it, and show that none of them are, Assume that the thing does exist, and show that this leads to a contradiction of the original assertion.

$\begingroup$ @Gary In the argument there are infinite rows, and each number contains infinite digits. These plus changing a number in each row creates a "new" number not on the "list." This assumes one could somehow "freeze" the infinite rows and columns to a certain state to change the digits, instead of infinity being a process that never ends.Cantor's theorem asserts that if is a set and () is its power set, i.e. the set of all subsets of ... For an elaboration of this result see Cantor's diagonal argument. The set of real numbers is uncountable, and so is the set of all infinite sequences of natural numbers.Cantor, Georg. ( b. St. Petersburg, Russia, 3 March 1845; d. Halle, Germany, 6 January 1918), mathematics, set theory. Cantor's father, Georg Waldemar Cantor, was a successful and cosmopolitan merchant. His extant letters to his son attest to a cheerfulness of spirit and deep appreciation of art and religion. His mother, Marie Böhm, was from ...Cantor attempted to prove that some infinite sets are countable and some are uncountable. All infinite sets are uncountable, and I will use Cantor's Diagonal Argument to produce a positive integer that can't be counted. Cantor's argument starts in a number grid in the upper left, extending...Cantor's diagonal argument, also called the diagonalisation argument, the diagonal slash argument or the diagonal method, was published in 1891 by Georg Cantor as a mathematical proof that there are infinite sets which cannot be put into one-to-one correspondence with the infinite set of natural numbers. Such sets are now known as uncountable ...

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In any event, Cantor's diagonal argument is about the uncountability of infinite strings, not finite ones. Each row of the table has countably many columns and there are countably many rows. That is, for any positive integers n, …About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new features NFL Sunday Ticket Press Copyright ...In my last post, I talked about why infinity shouldn't seem terrifying, and some of the interesting aspects you can consider without recourse to philosophy or excessive technicalities.Today, I'm going to explore the fact that there are different kinds of infinity. For this, we'll use what is in my opinion one of the coolest proofs of all time, originally due to Cantor in the 19th century.Cantor's diagonal argument is a general method to proof that a set is uncountable infinite. We basically solve problems associated to real numbers represented in decimal notation (digits with a decimal point if apply). However, this method is more general that it. Solve the following problem Problem Using the Cantor's diagonal method proof that ...Independent of Cantor's diagonal we know all cauchy sequences (and every decimal expansion is a limit of a cauchy sequence) converge to a real number. And we know that for every real number we can find a decimal expansion converging to it. And, other than trailing nines and trailing zeros, each decimal expansions are unique.

Cantor's Diagonal Argument: The maps are elements in N N = R. The diagonalization is done by changing an element in every diagonal entry. Halting Problem: The maps are partial recursive functions. The killer K program encodes the diagonalization. Diagonal Lemma / Fixed Point Lemma: The maps are formulas, with input being the codes of sentences.However, Cantor's diagonal argument shows that, given any infinite list of infinite strings, we can construct another infinite string that's guaranteed not to be in the list (because it differs from the nth string in the list in position n). You took the opposite of a digit from the first number.Wittgenstein’s “variant” of Cantor’s Diagonal argument – that is, of Turing’s Argument from the Pointerless Machine – is this. Assume that the function F’ is a development of one decimal fraction on the list, say, the 100th. The “rule for the formation” here, as Wittgenstein writes, “will run F (100, 100).”. But this.Cantor's theorem tells us that given a set there is always a set whose cardinality is larger. In particular given a set, its power set has a strictly larger cardinality. This means that there is no maximal size of infinity. ... In addition to showing a new interpretation to Cantor's Diagonal Argument, I also show that a one-to-one ...Cantor's diagonal theorem: P (ℵ 0) = 2 ℵ 0 is strictly gr eater than ℵ 0, so ther e is no one-to-one c orr esp ondenc e b etwe en P ( ℵ 0 ) and ℵ 0 . [2]Cantor's Diagonal Argument- Uncountable Set1 Answer. Denote by (xφl(k)) ( x φ l ( k)) a subsequence which works for Ml M l. In fact, you have to construct these subsequence by induction, in order to make (xφl+1(k)) ( x φ l + 1 ( k)) a subsequence of (xφl(k)) ( x φ l ( k)). Then we put xnk =xφk(k) x n k = x φ k ( k).The premise of the diagonal argument is that we can always find a digit b in the x th element of any given list of Q, which is different from the x th digit of that element q, and use it to construct a. However, when there exists a repeating sequence U, we need to ensure that b follows the pattern of U after the s th digit.Cantor's diagonal argument concludes the cardinality of the power set of a countably infinite set is greater than that of the countably infinite set. In other words, the …Mathematician Alexander Kharazishvili explores how powerful the celebrated diagonal method is for general and descriptive set theory, recursion theory, and Gödel's incompleteness theorem. ... The classical theory of Dedekind cuts is now embedded in the theory of Galois connections. 7 Cantor's construction of the real numbers is now ...Explanation of Cantor's diagonal argument.This topic has great significance in the field of Engineering & Mathematics field.

Cantor's Diagonal Argument is a proof by contradiction. In very non-rigorous terms, it starts out by assuming there is a "complete list" of all the reals, and then proceeds to show there must be some real number sk which is not in that list, thereby proving "there is no complete list of reals", i.e. the reals are uncountable.

I'm trying to grasp Cantor's diagonal argument to understand the proof that the power set of the natural numbers is uncountable. On Wikipedia, there is the following illustration: The explanation of the proof says the following: By construction, s differs from each sn, since their nth digits differ (highlighted in the example).You can use Cantor's diagonalization argument. Here's something to help you see it. If I recall correctly, this is how my prof explained it. Suppose we have the following sequences. 0011010111010... 1111100000101... 0001010101010... 1011111111111.... . . And suppose that there are a countable number of such sequences.We would like to show you a description here but the site won't allow us.Cantor's Diagonal Argument Recall that... • A set Sis nite i there is a bijection between Sand f1;2;:::;ng for some positive integer n, and in nite otherwise. (I.e., if it makes sense to count its elements.) • Two sets have the same cardinality i there is a bijection between them. (\Bijection", remember,A diagonally incrementing "snaking" function, from same principles as Cantor's pairing function, is often used to demonstrate the countability of the rational numbers. The graphical shape of Cantor's pairing function, a diagonal progression, is a standard trick in working with infinite sequences and countability.Cantor's Diagonal Argument. ] is uncountable. Proof: We will argue indirectly. Suppose f:N → [0, 1] f: N → [ 0, 1] is a one-to-one correspondence between these two sets. We intend …Disproving Cantor's diagonal argument Ask Question Asked 5 years, 6 months ago Modified 5 years, 6 months ago Viewed 1k times 2 I am familiar with Cantor's diagonal argument and how it can be used to prove the uncountability of the set of real numbers. However I have an extremely simple objection to make. Given the following:

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Cantor's diagonal argument. In set theory, Cantor's diagonal argument, also called the diagonalisation argument, the diagonal slash argument, the anti-diagonal argument, the diagonal method, and Cantor's diagonalization proof, was published in 1891 by Georg Cantor as a mathematical proof that there are infinite sets which cannot be put into one ...Georg Ferdinand Ludwig Philipp Cantor ( / ˈkæntɔːr / KAN-tor, German: [ˈɡeːɔʁk ˈfɛʁdinant ˈluːtvɪç ˈfiːlɪp ˈkantɔʁ]; 3 March [ O.S. 19 February] 1845 – 6 January 1918 [1]) was a mathematician. He played a pivotal role in the creation of set theory, which has become a fundamental theory in mathematics. Cantor established ...Cantor's diagonal argument, is this what it says? 6. how many base $10$ decimal expansions can a real number have? 5. Every real number has at most two decimal expansions. 3. What is a decimal expansion? Hot Network Questions Are there examples of mutual loanwords in French and in English?Cantor's diagonal argument is a paradox if you believe** that all infinite sets have the same cardinality, or at least if you believe** that an infinite set and its power set have the same cardinality. Cantor's diagonal argument is not a paradox if you use it to conclude that a set's cardinality is not that of its power set.Georg Ferdinand Ludwig Philipp Cantor (/ ˈ k æ n t ɔːr / KAN-tor, German: [ˈɡeːɔʁk ˈfɛʁdinant ˈluːtvɪç ˈfiːlɪp ˈkantɔʁ]; 3 March [O.S. 19 February] 1845 – 6 January 1918) was a mathematician.He played a pivotal role in the creation of set theory, which has become a fundamental theory in mathematics. Cantor established the importance of one-to-one …The canonical proof that the Cantor set is uncountable does not use Cantor's diagonal argument directly. It uses the fact that there exists a bijection with an uncountable set (usually the interval $[0,1]$). Now, to prove that $[0,1]$ is uncountable, one does use the diagonal argument. I'm personally not aware of a proof that doesn't use it.0. The proof of Ascoli's theorem uses the Cantor diagonal process in the following manner: since fn f n is uniformly bounded, in particular fn(x1) f n ( x 1) is bounded and thus, the sequence fn(x1) f n ( x 1) contains a convergent subsequence f1,n(x1) f 1, n ( x 1). Since f1,n f 1, n is also bounded then f1,n f 1, n contains a subsequence f2,n ...This problem has been solved! You'll get a detailed solution from a subject matter expert that helps you learn core concepts. Question: Functions from the set of NATURAL NUMBERS to (0,1). Use cantors diagonal method to prove. Prove that the following is uncountable using Cantor's diagonal method. Include every part of the method.I have a question about the potentially self-referential nature of cantor's diagonal argument (putting this under set theory because of how it relates to the axiom of choice). If we go along the denumerably infinite list of real numbers which theoretically exists for the sake of the example...What you should realize is that each such function is also a sequence. The diagonal arguments works as you assume an enumeration of elements and thereby create an element from the diagonal, different in every position and conclude that that element hasn't been in the enumeration.Diagonal arguments have been used to settle several important mathematical questions. There is a valid diagonal argument that even does what we'd originally set out to do: prove that \(\mathbb{N}\) and \(\mathbb{R}\) are not equinumerous. ... Cantor's theorem guarantees that there is an infinite hierarchy of infinite cardinal numbers. Let ... ….

B Another consequence of Cantor's diagonal argument. Aug 23, 2020; 2. Replies 43 Views 3K. I Cantor's diagonalization on the rationals. Aug 18, 2021; Replies 25 Views 2K. B One thing I don't understand about Cantor's diagonal argument. Aug 13, 2020; 2. Replies 55 Views 4K. I Regarding Cantor's diagonal proof.The proof of Theorem 9.22 is often referred to as Cantor’s diagonal argument. It is named after the mathematician Georg Cantor, who first published the proof in 1874. Explain the connection between the winning strategy for Player Two in Dodge Ball (see Preview Activity 1) and the proof of Theorem 9.22 using Cantor’s diagonal argument. AnswerJan 21, 2021 · The diagonal process was first used in its original form by G. Cantor. in his proof that the set of real numbers in the segment $ [ 0, 1 ] $ is not countable; the process is therefore also known as Cantor's diagonal process. A second form of the process is utilized in the theory of functions of a real or a complex variable in order to isolate ... Cantor's diagonal proof of the uncountability of the reals is usually the only proof they can comprehend. $\endgroup$ - Keshav Srinivasan. Feb 19, 2014 at 15:13 $\begingroup$ @KeshavSrinivasan: Apperently you are complaining it is just another proof they cannot comprehend. Note that the only "set theory" really used is that one can define a ...S is countable (because of the latter assumption), so by Cantor's diagonal argument (neatly explained here) one can define a real number O that is not an element of S. But O has been defined in finitely many words! Here Poincaré indicates that the definition of O as an element of S refers to S itself and is therefore impredicative.Georg Ferdinand Ludwig Philipp Cantor (/ ˈ k æ n t ɔːr / KAN-tor, German: [ˈɡeːɔʁk ˈfɛʁdinant ˈluːtvɪç ˈfiːlɪp ˈkantɔʁ]; 3 March [O.S. 19 February] 1845 - 6 January 1918) was a mathematician.He played a pivotal role in the creation of set theory, which has become a fundamental theory in mathematics. Cantor established the importance of one-to-one correspondence between ...As for the second, the standard argument that is used is Cantor's Diagonal Argument. The punchline is that if you were to suppose that if the set were countable then you could have written out every possibility, then there must by necessity be at least one sequence you weren't able to include contradicting the assumption that the set was ...Cantor's diagonal theorem: P (ℵ 0) = 2 ℵ 0 is strictly gr eater than ℵ 0, so ther e is no one-to-one c orr esp ondenc e b etwe en P ( ℵ 0 ) and ℵ 0 . [2]REAL ANALYSIS (COUNTABILITY OF SETS)In this video we will discuss Cantor's Theorem with proof.Countability of Sets | Similar Sets, Finite Sets, Infinite Sets... Cantors diagonal, To provide a counterexample in the exact format that the "proof" requires, consider the set (numbers written in binary), with diagonal digits bolded: x[1] = 0. 0 00000... x[2] = 0.0 1 1111..., Cantor's Diagonal Argument ] is uncountable. Proof: We will argue indirectly. Suppose f:N → [0, 1] f: N → [ 0, 1] is a one-to-one correspondence between these two sets. We intend to argue this to a contradiction that f f cannot be "onto" and hence cannot be a one-to-one correspondence -- forcing us to conclude that no such function exists., Cantor's diagonal argument shows that any attempted bijection between the natural numbers and the real numbers will necessarily miss some real numbers, and therefore cannot be a valid bijection. While there may be other ways to approach this problem, the diagonal argument is a well-established and widely used technique in mathematics for ..., The premise of the diagonal argument is that we can always find a digit b in the x th element of any given list of Q, which is different from the x th digit of that element q, and use it to construct a. However, when there exists a repeating sequence U, we need to ensure that b follows the pattern of U after the s th digit., In order for Cantor's construction to work, his array of countably infinite binary sequences has to be square. If si and sj are two binary sequences in the..., Jan 21, 2021 · The diagonal process was first used in its original form by G. Cantor. in his proof that the set of real numbers in the segment $ [ 0, 1 ] $ is not countable; the process is therefore also known as Cantor's diagonal process. A second form of the process is utilized in the theory of functions of a real or a complex variable in order to isolate ... , Base 1 is just an encoding. It represents a number but it isn't the number. Cantor's diagonal wouldn't work on base 1 encodings, because there are only a countable number of them, but you can't encode all numbers in base 1 anyway so this shows nothing other than that there are only countably many base 1 strings., 126. 13. PeterDonis said: Cantor's diagonal argument is a mathematically rigorous proof, but not of quite the proposition you state. It is a mathematically rigorous proof that the set of all infinite sequences of binary digits is uncountable. That set is not the same as the set of all real numbers., $\begingroup$ You have to show (or at least mention) that the $000\ldots$ part of these terminating decimals starts early enough for the zeroes to be included in the diagonal. Then you have to show that the diagonal can't all be zeroes, by showing that the $111\ldots$ part of those non-terminating decimals starts early enough for the ones to be included in the diagonal., Probably every mathematician is familiar with Cantor's diagonal argument for proving that there are uncountably many real numbers, but less well-known is the proof of the existence of an undecidable problem in computer science, which also uses Cantor's diagonal argument. I thought it was really cool when I first learned it last year., 24 ຕ.ລ. 2011 ... Another way to look at it is that the Cantor diagonalization, treated as a function, requires one step to proceed to the next digit while ..., Cantor’s diagonal argument, the rational open interv al (0, 1) would be non-denumerable, and we would ha ve a contradiction in set theory , because Cantor also prov ed the set of the rational ..., This article discusses two theorems of Georg Cantor: Cantor's Little Theorem and Cantor's Diagonal Theorem. The results are obtained by generalizing the method of proof of the well known Cantor's theorem about the cardinalities of a set and its power set. As an application of these, Gödel's first incompleteness theorem is proved. Hints are given as to how to derive other deeper ..., Use Cantor's diagonal argument to show that the set of all infinite sequences of the letters a, b, c, and d are uncountably infinite. This problem has been solved! You'll get a detailed solution from a subject matter expert that helps you learn core concepts., The proof is one of mathematics' most famous arguments: Cantor's diagonal argument [8]. The argument is developed in two steps . Let \(T\) be the set of semi-infinite sequences formed by the digits 0 and 2. An element \(t \in T\) has the form \(t = t_{1}t_{2}t_{3} \dots\) where \(t_{i} \in \{0, 2\}\). The first step of the proof is to prove ..., Cantor's Diagonal Argument - Rational. 0. Cantor's diagonalization- why we must add $2 \pmod {10}$ to each digit rather than $1 \pmod {10}$? Hot Network Questions Questions on reading the prologue of Aesopus Latinus via LLPSI Are there examples of mutual loanwords in French and in English? Do fighter pilots have to manually input the ordnance ..., I have found that Cantor’s diagonalization argument doesn’t sit well with some people. It feels like sleight of hand, some kind of trick. Let me try to outline some of the ways it could be a trick. You can’t list all integers One argument against Cantor is that you can never finish writing z because you can never list all of the integers., Cantor Diagonal Argument -- from Wolfram MathWorld. Algebra Applied Mathematics Calculus and Analysis Discrete Mathematics Foundations of Mathematics Geometry History and Terminology Number Theory Probability and Statistics Recreational Mathematics Topology. Alphabetical Index New in MathWorld. Foundations of Mathematics. Set Theory., Proof: We use Cantor's diagonal argument. So we assume (toward a contradiction) that we have an enumeration of the elements of S, say as S = fs 1;s 2;s 3;:::gwhere each s n is an in nite sequence of 0s and 1s. We will write s 1 = s 1;1s 1;2s 1;3, s 2 = s 2;1s 2;2s 2;3, and so on; so s n = s n;1s n;2s n;3. So we denote the mth element of s n ..., P6 The diagonal D= 0.d11d22d33... of T is a real number within (0,1) whose nth decimal digit d nn is the nth decimal digit of the nth row r n of T. As in Cantor's diagonal argument [2], it is possible to define another real number A, said antidiagonal, by replacing each of the infinitely many decimal digits of Dwith a different decimal digit., In this guide, I'd like to talk about a formal proof of Cantor's theorem, the diagonalization argument we saw in our very first lecture., Step 3 - Cantor's Argument) For any number x of already constructed Li, we can construct a L0 that is different from L1, L2, L3...Lx, yet that by definition belongs to M. For this, we use the diagonalization technique: we invert the first member of L1 to get the first member of L0, then we invert the second member of L2 to get the second member ..., If you're referring to Cantor's diagonal argument, it hinges on proof by contradiction and the definition of countability. Imagine a dance is held with two separate schools: the natural numbers, A, and the real numbers in the interval (0, 1), B. If each member from A can find a dance partner in B, the sets are considered to have the same ..., In this section, I want to briefly remind about Cantor’s diagonal argument, which is a short proof of why there can’t exist 1-to-1 mapping between all elements of a countable and an uncountable infinite sets. The proof takes all natural numbers as the countable set, and all possible infinite series of decimal digits as the uncountable set., Cantor's diagonal proof is not infinite in nature, and neither is a proof by induction an infinite proof. For Cantor's diagonal proof (I'll assume the variant where we show the set of reals between $0$ and $1$ is uncountable), we have the following claims:, Meanwhile, Cantor's diagonal method on decimals smaller than the 1s place works because something like 1 + 10 -1 + 10 -2 + .... is a converging sequence that corresponds to a finite-in-magnitude but infinite-in-detail real number. Similarly, Hilbert's Hotel doesn't work on the real numbers, because it misses some of them., I find Cantor's diagonal argument to be in the realm of fuzzy logic at best because to build the diagonal number it needs to go on forever, the moment you settle for a finite number then this number already was in the set of all numbers. So how can people be sure about the validity of the diagonal argument when it is impossible to pinpoint a number that isn't in the set of all numbers ?, My thinking is (and where I'm probably mistaken, although I don't know the details) that if we assume the set is countable, ie. enumerable, it shouldn't make any difference if we replace every element in the list with a natural number. From the perspective of the proof it should make no..., Yes, because Cantor's diagonal argument is a proof of non existence. To prove that something doesn't, or can't, exist, you have two options: Check every possible thing that could be it, and show that none of them are, Assume that the thing does exist, and show that this leads to a contradiction of the original assertion., In any event, Cantor's diagonal argument is about the uncountability of infinite strings, not finite ones. Each row of the table has countably many columns and there are countably many rows. That is, for any positive integers n, …, As for the second, the standard argument that is used is Cantor's Diagonal Argument. The punchline is that if you were to suppose that if the set were countable then you could have written out every possibility, then there must by necessity be at least one sequence you weren't able to include contradicting the assumption that the set was ..., Cantor’s diagonal argument, the rational open interv al (0, 1) would be non-denumerable, and we would ha ve a contradiction in set theory , because Cantor also prov ed the set of the rational ..., 1. The Cantor's diagonal argument works only to prove that N and R are not equinumerous, and that X and P ( X) are not equinumerous for every set X. There are variants of the same idea that will help you prove other things, but "the same idea" is a pretty informal measure. The best one can really say is that the idea works when it works, and if ...