1; where _All hollow-horned animals are ruminants_, but we can only say that _Some ruminants are hollow-horned_.
That I.may be simply converted may be seen in Fig.

3, which represents the least that an I.proposition can mean; and that E.may be simply converted is manifest in Fig.

4.
As for O., we know that it cannot be converted, and this is made plain enough by glancing at Fig.

1; for that represents the O., _Some ruminants are not hollow-horned_, but also shows this to be compatible with _All hollow-horned animals are ruminants_ (A.).

Now in conversion there is (by definition) no change of quality.