Let $D$ be an effectively generated set of recursive ordinals the contains $0$ and that is closed under an effectively defined ordinal successor function "$+1$" and that have a well defined relation of ordinal strict smaller than relation $<$ on it, such that no two distinct elements of $D$ have the same order type. We'll simply label such a set as an "effective set of recursive ordinals"
Define recursively
- $T_0 = T$,
- $T_{i+1} = T_i + \operatorname{Con}(T_i)$ for every $i \in D$,
- $T_j = \bigcup\{T_i\mid i<j\}$ for every limit ordinal $j \in D $.
Where $T$ is an extension of $PA$.
Say that $T$ is $D$_ultraconsistent iff $\forall i \in D \ ( \operatorname{Con}(T_i)) $
Say that $T$ is ultraconsistent iff
$\forall D (D$ is an effective set of recursive ordinals$ \implies T $ is $D$_ultraconsistent$)$
Do the following statements follow?
If $T,H$ are ultraconsistent then $T \cup H$ is ultraconsistent.
If $T$ is ultraconsistent and $G$ is a fragment of $T$ then $G$ is ultraconsistent.
Can we have a theory $T$ that is ultraconsistent and yet $FALSE$?