A.Prakriti, the cause of ignorance, is made up of three Gunas, and carries with her the
reflection of that transcendent Reality, Satchidananda. This Prakriti is divided into two aspects,
called Maya and Avidya. Maya is Suddha-Sattva-Pradhana or that state of Prakriti in which the
principle of Purity or Sattva, predominates over the other two,—Rajas and Tamas. Avidya is
Malina-Sattva or that state of Prakriti in which Sattva is predominated and sullied by the other two.
When that pure Intelligence, Chit, is reflected through Maya or Suddha-Sattva, the reflected
Consciousness is called Isvara. It is one only, and controls Maya. When that Chit is reflected in
Malina-Sattva or Avidya, the reflected Consciousness is called Jiva. Due to the multifarious nature
of Avidya, Jivas are too many, and being individualised and separated from one another, they are
swayed by Avidya or ignorance. And this ignorance leads them to identification with the five
sheaths and the three bodies. Thus, there is activity, pain and suffering for the Jiva.
In the sentence, Tat Tvam Asi, Tat refers to the reflected Consciousness in Maya and Tvam
refers to the reflected Consciousness in Avidya. The word Asi proclaims their unity. It asserts that
one Chit alone, reflected in a twofold way, goes under the names of Isvara and Jiva, when it is
respectively qualified by the Upadhis of Maya and Avidya in its reflected State.
B.The reflection of a face in a mirror is different from the face; the reflection imitates the mirror inasmuch as it possesses the property of being in the mirror and the quality of the mirror. The reflection depends on the mirror for its existence. But the real face does not. So, the real face is different from the reflection. Similarly, the reflection of the Self in the ego is different from the Pure Self. In the case of the face, the face is real but not its reflection in the mirror. The reflection is not always there. But, at the same time, the reflection is not totally unreal since it is seen at times. Hence, the reflection is indescribable and the face is different from it. In the case of the Pure Self and Its reflection, in fact, however, both of them are devoid of any real distinction, in the case of the face and the mirror, the mirror has an existence independent of the face. But, in the case of the Pure Self, the intellect which is the reflecting medium is not having an independent existence all by itself, apart from the existence of the Pure Self. Therefore, the distinction between the Pure Self and Its reflection is only apparent and not real. Owing to a non-discrimination due to ignorance between the Pure Self and Its reflection, the Self is regarded as an individual suffering transmigratory existence.
It may be said that the reflection of the Self in the ego, as distinct from the Pure Self, is the individual soul experiencing and acting in this universe, on the authority that the individual soul is a real entity having its own properties like the shadow of a tree having the property of refreshing anyone coming under it on a hot midday. That cannot be so. The refreshing property cannot be attributed to the shadow, for it is the effect of refraining from the warm things, say, the hot sun.
Further, because of that, it cannot be said that the refreshing property that is seen in the shadow is ample proof for accepting the reality of the shadow. One is not refreshed by sitting close to a burning hearth under its shadow.
The reflection of the face in the mirror is neither the property of the face nor the property of the mirror. If it were the property of either of the two, then, it should continue to exist when one of
the two is not there. If it can be said that the reflection is the property of both the real face and the mirror, it can be equally refuted by saying that even when both the mirror and the face are there but improperly placed, the reflection is not seen.
Reference & Courtesy: Vedanta for beginners - Shri Swami Sivananda