With an I proposition neither term is distributed.Thus care must be used lest an undistributed term in the convertend be distributed in the converse. Illustrations:
| Convertend. | Converse. |
| Some men are wise. | Some wise beings are men. |
| Some teachers scold. | Some who scold are teachers. |
| Some high school graduates enter college. | Some who enter college are high school graduates. |
| Some Americans live simply. | Some who live simply are Americans. |
From the foregoing we conclude first, that I is converted simply; second, that I is converted into I.
The O Proposition.
With an O proposition the subject is undistributed while the predicate is distributed. This condition presents a peculiar difficulty. Consider, for example, the O proposition, “Some men are not wise.” Convert this into, “Some wise beings are not men,” and the undistributed subject of the convertend, which is “men,” becomes the distributed predicate of the converse. Thus the O proposition cannot be converted without violating the rule for distribution.
A Summary of How the Four Logical Propositions May be Converted.
1. A. The ordinary A proposition may be converted by limitation only. The co-extensive A may be converted simply.
2. E. The E proposition is converted simply. The E may also be converted by limitation, but the inference thus obtained is weakened.
3. I. The I proposition may be converted simply only.
4. O. The O proposition cannot be converted.