Category:Axiom of Replacement

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This category contains results about Axiom of Replacement.

Set Theory

For every mapping $f$ and subset $S$ of the domain of $f$, there exists a set containing the image $f \sqbrk S$.

More formally, let us express this as follows:


Let $\map P {x, z}$ be a propositional function, which determines a mapping.

That is, we have:

$\forall x: \exists ! y : \map P {x, y}$.

Then we state as an axiom:

$\forall A: \exists B: \forall y: \paren {y \in B \iff \exists x \in A : \map P {x, y} }$


Class Theory

For every mapping $f$ and set $x$ in the domain of $f$, the image $f \sqbrk x$ is a set.