The mental permanent atom is found on the first sub-plane of the mental plane and is together with the buddhic permanent atom and the atmic permanent atom part of the soul, or 'the ego' as the soul is sometimes called in the ageless wisdom. The mental permanent atom can be considered as the substance germ of the abstract mind.2
The mental unit can be considered as the substance germ of the concrete mind and is found on the fourth sub-plane of the mental plane. Together with the astral permanent atom and the physical permanent atom it is part of the personality. As substance germs of relative permanence3 the latter three are contained in the egoic body, or the egoic lotus, which is found on the third sub-plane of the mental plane.