We have to supply 'on account of designation' from the preceding Sûtra.
Because the text designates the highest Self as something different from
the individual Self in the state of deep sleep as well as at the time of
departure, the highest Self is thus different. For the Vâjasaneyaka,
after having introduced the individual Self in the passage 'Who is that
Self?--He who consisting of knowledge is among the prânas,' &c. (_Bri_.
Up. IV, 3, 7), describes how, in the state of deep sleep, being not
conscious of anything it is held embraced by the all-knowing highest
Self, embraced by the intelligent Self it knows nothing that is without,
nothing that is within' (IV, 3, 21). So also with reference to the time
of departure, i.e. dying 'Mounted by the intelligent Self it moves along
groaning' (IV, 3, 35). Now it is impossible that the unconscious
individual Self, either lying in deep sleep or departing from the body,
should at the same time be embraced or mounted by itself, being all-
knowing. Nor can the embracing and mounting Self be some other
individual Self; for no such Self can be all-knowing.--The next Sûtra
supplies a further reason.