The (Vedic) assertion (that "all things become known when the one is known") can remain unaffected only if all the effects are non-different from Brahman; and this is confirmed by Vedic texts.
ॐ antara vijñanamanasi kramena talliṅgaditi cennavisesat ॐ || 2.3.15||
If it be contended that the intellect and mind must find accommodation in some order in some intermediate stage, because indicatory marks of their existence are in evidence, then not so, because their presence creates no difference (ie., does not disturb the order of creation or dissolution).
The mention of birth and death must be in the primary sense in relation to the moving and the motionless; in relation to the soul it must be in a secondary sense, the application (of such words) being possible when a body is present.
The individual soul has no origin; because the Upanishads do not mention this, because its eternality is known from them and (because of other reasons).
(The individual soul must be atomic in dimension owing to the mention in the Vedas) of its departure from the body, going (to the next world by following a course) and coming back (from there).
If it be objected that the soul is not atomic because its size is heard of as not being so, we reply, no, since that context relates to the other (ie., the supreme Self).
If it be objected that (the argument holds good in the case of sandal paste) owing to its peculiarity of position, (but that is not evident in the case of the soul), then we say, no, (a peculiar location) for the soul is admitted in the Upanishads, for it exists in the heart.
ॐ यावदात्मभावित्वाच्च न दोषस्तद्दर्शनात् ॐ ॥ २.३.३०॥
ॐ yavadatmabhavitvacca na dosastaddarsanat ॐ || 2.3.30||
And because the contact between the soul and the intellect persists so long as the worldly state of the soul continues, there can be no defect, for this is what is met with in the scriptures.
Rather because that contact (with the intellect etc.,) which remains latent (in sleep and dissolution) can become manifest (during waking and creation) like manhood
Else (if the existence of the internal organ be not admitted) there will be the possibility of either constant perception or non-perception or it will have to be admitted that either of the powers (of the soul or of the organs) becomes (suddenly) debarred (or delimited or lost).
(The individual souls are) parts of God because of the mention that they are different, also because some read otherwise of (Brahman's) identity with fishermen, slaves, gamblers and others.
The Supreme Self is not so (touched by the suffering of the individual soul), even as light etc., are not (affected by the things that condition them).
(Even the unseen potential results of works cannot regulate individual allocation), since the unseen potential results (themselves) cannot be allocated thus.
If it be said that this (individual allocation of pleasure and pain) can be possible in accordance with the separate part (of each soul in each body), then it cannot be so, because of all (the omnipresent souls) getting included in all (the bodies).