The wholeness axioms, proposed by Paul Corazza
{% cite Corazza2000 Corazza2003 %}, occupy a high place in the
upper stratosphere of the large cardinal hierarchy, intended as slight
weakenings of the [](Kunen_inconsistency.md),
but similar in spirit.
The **wholeness axioms** are formalized in the language $\{\in,j\}$,
augmenting the usual language of set theory $\{\in\}$ with an
additional unary function symbol $j$ to represent the [](Elementary%20embedding.md).
The base theory ZFC is expressed only in the smaller language
$\{\in\}$. Corazza's original proposal, which we denote by
$\text{WA}_0$, asserts that $j$ is a nontrivial amenable elementary
embedding from the universe to itself, without adding formulas
containing $j$ to the separation and replacement axioms. Elementarity is
expressed by the scheme $\varphi(x)\iff\varphi(j(x))$, where
$\varphi$ runs through the formulas of the usual language of set
theory; nontriviality is expressed by the sentence $\exists x
j(x)\not=x$; and amenability is simply the assertion that
$j\upharpoonright A$ is a set for every set $A$. Amenability in this
case is equivalent to the assertion that the separation axiom holds for
$\Delta_0$ formulae in the language $\{\in,j\}$. The **wholeness
axiom** $\text{WA}$, also denoted $\text{WA}_\infty$, asserts in
addition that the full separation axiom holds in the language
$\{\in,j\}$.
Those two axioms are the endpoints of the hierarchy of axioms
$\text{WA}_n$, asserting increasing amounts of the separation axiom.
Specifically, the wholeness axiom $\text{WA}_n$, where $n$ is amongst
$0,1,\ldots,\infty$, consists of the following:
1. (elementarity) All instances of $\varphi(x)\iff\varphi(j(x))$ for
$\varphi$ in the language $\{\in,j\}$.
2. (separation) All instances of the Separation Axiom for $\Sigma_n$
formulae in the full language $\{\in,j\}$.
3. (nontriviality) The axiom $\exists x\,j(x)\not=x$.
Clearly, this resembles the [](Kunen_inconsistency.md).
What is missing from the wholeness axiom schemes, and what figures
prominantly in Kunen's proof, are the instances of the replacement axiom
in the full language with $j$. In particular, it is the replacement
axiom in the language with $j$ that allows one to define the critical
sequence $\langle \kappa_n\mid n\lt\omega\rangle$, where
$\kappa_{n+1}=j(\kappa_n)$, which figures in all the proofs of the
Kunen inconsistency. Thus, none of the proofs of the Kunen inconsistency
can be carried out with $\text{WA}$, and indeed, in every model of
$\text{WA}$ the critical sequence is unbounded in the ordinals.
The hiearchy of wholeness axioms is strictly increasing in strength, if
consistent. {% cite Hamkins2001 %}
If $j:V_\lambda\to V_\lambda$ witnesses a [](Rank_into_rank.md)
cardinal, then $\langle V_\lambda,\in,j\rangle$ is a model of the
wholeness axiom.
**Axioms $\mathrm{I}_4^n$** for natural numbers $n$ (starting from
$0$) are an attempt to measure the gap between $\mathrm{I}_3$ and
$\mathrm{WA}$. Each of these axioms asserts the existence of a
transitive model of $\mathrm{ZFC} + \mathrm{WA}$ with additional,
stronger and stronger properties. Namely, $\mathrm{I}_4^n(\kappa)$
holds if and only if there is a transitive model $(M,\in,j)$ of
$\mathrm ZFC+WA$ with $V_{j^n(\kappa)+1}\subseteq M$ and $\kappa$
the critical point of $j$. $\mathrm{I}_3(κ)$ is equivalent to the
existence of an $\mathrm{I}_4(κ)$-coherent set of embeddings. On the
other hand, it is not known whether the $\mathrm{I}_4^n$ axioms really
increase in consistency strength and whether it is possible in
$\mathrm{ZFC}$ that $\forall _{n\in\omega} \mathrm{I}_4^n(κ)
\land \neg
\mathrm{I}_3(κ)$.{% cite Corazza2003 %}
If the wholeness axiom is consistent with $\text{ZFC}$, then it is
consistent with
$\text{ZFC+V=HOD}$.{% cite Hamkins2001 %}