We have the following indirect implication of form equivalence classes:
| Implication | Reference |
|---|---|
| 63 \(\Rightarrow\) 70 | clear |
| 70 \(\Rightarrow\) 206 | clear |
Here are the links and statements of the form equivalence classes referenced above:
| Howard-Rubin Number | Statement |
|---|---|
| 63: |
\(SPI\): Weak ultrafilter principle: Every infinite set has a non-trivial ultrafilter.
|
| 70: | There is a non-trivial ultrafilter on \(\omega\). Jech [1973b], prob 5.24. |
| 206: | The existence of a non-principal ultrafilter: There exists an infinite set \(X\) and a non-principal ultrafilter on \(X\). |
Comment: