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Q&A Existence of a set of all sets

posted 4y ago by MathPhysics‭  ·  edited 4y ago by MathPhysics‭

Answer
#8: Post edited by user avatar MathPhysics‭ · 2020-10-09T09:43:06Z (about 4 years ago)
  • Let $V$ be a set of all sets. According to the **Axiom Schema of Comprehension**, we can have the following set:
  • $$U= \\{ x\in V \mid x \not \in x \\}.$$
  • Now, there are two cases:
  • - $U \in U$, which, according to the definition of the set $U$, implies that $U \not \in U$, which is a contradiction;
  • - $U \not \in U$, which, according to the definition of the set $U$, implies that $U \in U$, which is a contradiction.
  • Thus, a set of all sets cannot exist in such an axiomatic system.
  • $$\begin{CD} A @>a>> B \\\\ @V b V V= @VV c V \\\\ C @>>d> D \end{CD}$$
  • Let $V$ be a set of all sets. According to the **Axiom Schema of Comprehension**, we can have the following set:
  • $$U= \\{ x\in V \mid x \not \in x \\}.$$
  • Now, there are two cases:
  • - $U \in U$, which, according to the definition of the set $U$, implies that $U \not \in U$, which is a contradiction;
  • - $U \not \in U$, which, according to the definition of the set $U$, implies that $U \in U$, which is a contradiction.
  • Thus, a set of all sets cannot exist in such an axiomatic system.
#7: Post edited by user avatar MathPhysics‭ · 2020-10-09T09:42:38Z (about 4 years ago)
  • Let $V$ be a set of all sets. According to the **Axiom Schema of Comprehension**, we can have the following set:
  • $$U= \\{ x\in V \mid x \not \in x \\}.$$
  • Now, there are two cases:
  • - $U \in U$, which, according to the definition of the set $U$, implies that $U \not \in U$, which is a contradiction;
  • - $U \not \in U$, which, according to the definition of the set $U$, implies that $U \in U$, which is a contradiction.
  • Thus, a set of all sets cannot exist in such an axiomatic system.
  • Let $V$ be a set of all sets. According to the **Axiom Schema of Comprehension**, we can have the following set:
  • $$U= \\{ x\in V \mid x \not \in x \\}.$$
  • Now, there are two cases:
  • - $U \in U$, which, according to the definition of the set $U$, implies that $U \not \in U$, which is a contradiction;
  • - $U \not \in U$, which, according to the definition of the set $U$, implies that $U \in U$, which is a contradiction.
  • Thus, a set of all sets cannot exist in such an axiomatic system.
  • $$\begin{CD} A @>a>> B \\\\ @V b V V= @VV c V \\\\ C @>>d> D \end{CD}$$
#6: Post edited by user avatar MathPhysics‭ · 2020-10-09T09:29:49Z (about 4 years ago)
  • $$\begin{pmatrix} 1 & 2 \\\\ 3 & 4 \end{pmatrix}$$
  • Let $V$ be a set of all sets. According to the **Axiom Schema of Comprehension**, we can have the following set:
  • $$U= \\{ x\in V \mid x \not \in x \\}.$$
  • Now, there are two cases:
  • - $U \in U$, which, according to the definition of the set $U$, implies that $U \not \in U$, which is a contradiction;
  • - $U \not \in U$, which, according to the definition of the set $U$, implies that $U \in U$, which is a contradiction.
  • Thus, a set of all sets cannot exist in such an axiomatic system.
#5: Post edited by user avatar MathPhysics‭ · 2020-10-09T09:29:06Z (about 4 years ago)
  • $$\require{AMScd}\begin{CD} A @>a>> B \\\\ @V b V V= @VV c V \\\\ C @>>d> D \end{CD}$$
  • $$\begin{pmatrix} 1 & 2 \\\\ 3 & 4 \end{pmatrix}$$
#4: Post edited by user avatar MathPhysics‭ · 2020-10-09T09:27:57Z (about 4 years ago)
  • $$\overbrace{x+y+z}$$
  • Let $V$ be a set of all sets. According to the **Axiom Schema of Comprehension**, we can have the following set:
  • $$U= \\{ x\in V \mid x \not \in x \\}.$$
  • Now, there are two cases:
  • - $U \in U$, which, according to the definition of the set $U$, implies that $U \not \in U$, which is a contradiction;
  • - $U \not \in U$, which, according to the definition of the set $U$, implies that $U \in U$, which is a contradiction.
  • Thus, a set of all sets cannot exist in such an axiomatic system.
  • $$\require{AMScd}\begin{CD} A @>a>> B \\\\ @V b V V= @VV c V \\\\ C @>>d> D \end{CD}$$
#3: Post edited by user avatar MathPhysics‭ · 2020-10-09T09:26:01Z (about 4 years ago)
  • $$\require{AMScd}\begin{CD} A @>a>> B \\\\ @V b V V= @VV c V \\\\ C @>>d> D \end{CD}$$
  • $$\overbrace{x+y+z}$$
  • Let $V$ be a set of all sets. According to the **Axiom Schema of Comprehension**, we can have the following set:
  • $$U= \\{ x\in V \mid x \not \in x \\}.$$
  • Now, there are two cases:
  • - $U \in U$, which, according to the definition of the set $U$, implies that $U \not \in U$, which is a contradiction;
  • - $U \not \in U$, which, according to the definition of the set $U$, implies that $U \in U$, which is a contradiction.
  • Thus, a set of all sets cannot exist in such an axiomatic system.
  • $$\overbrace{x+y+z}$$
  • Let $V$ be a set of all sets. According to the **Axiom Schema of Comprehension**, we can have the following set:
  • $$U= \\{ x\in V \mid x \not \in x \\}.$$
  • Now, there are two cases:
  • - $U \in U$, which, according to the definition of the set $U$, implies that $U \not \in U$, which is a contradiction;
  • - $U \not \in U$, which, according to the definition of the set $U$, implies that $U \in U$, which is a contradiction.
  • Thus, a set of all sets cannot exist in such an axiomatic system.
#2: Post edited by user avatar MathPhysics‭ · 2020-10-09T09:25:06Z (about 4 years ago)
  • Let $V$ be a set of all sets. According to the **Axiom Schema of Comprehension**, we can have the following set:
  • $$U= \\{ x\in V \mid x \not \in x \\}.$$
  • Now, there are two cases:
  • - $U \in U$, which, according to the definition of the set $U$, implies that $U \not \in U$, which is a contradiction;
  • - $U \not \in U$, which, according to the definition of the set $U$, implies that $U \in U$, which is a contradiction.
  • Thus, a set of all sets cannot exist in such an axiomatic system.
  • $$\require{AMScd}\begin{CD} A @>a>> B \\\\ @V b V V= @VV c V \\\\ C @>>d> D \end{CD}$$
  • $$\overbrace{x+y+z}$$
  • Let $V$ be a set of all sets. According to the **Axiom Schema of Comprehension**, we can have the following set:
  • $$U= \\{ x\in V \mid x \not \in x \\}.$$
  • Now, there are two cases:
  • - $U \in U$, which, according to the definition of the set $U$, implies that $U \not \in U$, which is a contradiction;
  • - $U \not \in U$, which, according to the definition of the set $U$, implies that $U \in U$, which is a contradiction.
  • Thus, a set of all sets cannot exist in such an axiomatic system.
#1: Initial revision by user avatar MathPhysics‭ · 2020-10-09T08:45:20Z (about 4 years ago)
Let $V$ be a set of all sets. According to the **Axiom Schema of Comprehension**, we can have the following set:

$$U= \\{ x\in V \mid x \not \in x \\}.$$

Now, there are two cases:

- $U \in U$, which, according to the definition of the set $U$, implies that $U \not \in U$, which is a contradiction;

- $U \not \in U$, which, according to the definition of the set $U$, implies that $U \in U$, which is a contradiction.

Thus, a set of all sets cannot exist in such an axiomatic system.