However...

However, the fourth kind, that is, the addition of a substantial part without the destruction of another part, can be called ‘generation without corruption.’ And the reverse may be said of the fifth type, that is, the destruction of a substantial part without the appearance of a part to replace it, can be called ‘corruption without generation.’ Likewise, the eighth kind, the appearance of new accidents, can be considered ‘generation without corruption’ and the ninth kind, the destruction of accidents, can be considered ‘corruption without generation.’ The attachment of the soul to the body can also be considered a kind of generation, in view of the fact that the attribute of life thereby appears in the body.

The reverse, dying, can be considered a kind of corruption, in view of the fact that the life of the body is destroyed, though not in the sense that the spirit is destroyed, for the spirit is indestructible.

Whether or not generation without corruption can be imagined in types four and fourteen, and corruption without generation in types five and fifteen, hinges on whether the presence of two forms in a single matter is considered permissible and on whether it is held that the prior form remains when a new substantial form appears, and in the case of the destruction of a higher form, whether the lower form existed together with the higher form and continues.

If we hold that two forms cannot be present in a single thing, then we will be compelled to hold, in types four and fourteen, that the earlier form is destroyed, and in types five and fifteen that a new form is freshly brought about. In this case these types will also be considered types of generation and corruption, not as cases of mere generation and mere corruption.

Therefore, the problem which must be investigated is whether the presence of two forms in a single thing is permitted so that the assumption of the occurrence of two actual substantial forms in a potential existent and the continuation of one of them in an actual existent is allowed in cases five and fifteen, and the presence of two substantial forms in an actual existent and the persistence of the earlier form in types four and fourteen may be correct.