Bhagavad Gita says: ~ "Don't unsettle the minds of ignorant by revealing the esoteric truth.”
One could go on and on, but the point is that the Upanishads approach the Supreme immutable truth in multiple ways and try to articulate the manifest and unmanifest aspects of the Brahman.
Sage Sri, Goudpada: ~ To establish the truth of Non-duality by sheer reasoning alone. He begins by defining "What is real?" "What is unreal?" etc, because that is the right way to discuss or teach. People must first know what they are talking about. (Mandukya Karika)
Reasoning is interpretable in two ways. The egocentric interpretation is to apply it only to waking experience. The Soulcentric interpretation is to apply it to the three states. The latter leads to the final settlement of the problems because it takes all data into consideration.
As we keep digging deeper and deeper, the truth will shine as pure awareness in the midst of the duality (waking).
The Soul, the innermost Self is our ultimate teacher. It is only our inner teacher that will walk with us to the goal, for the Soul is the goal. From ultimate standpoint there is no teacher, there is no teaching and there is no student.
Millions are searching for the truth, but one in million will realize it. For those that are deluded, the multiple points of view may amount to contradictory perceptions but Upanishads are the epitome of an attempted understanding of the immortal, immutable Brahman by mortals caught in the dynamism of this universe in which we exist.
Why distinction should imply the contradiction. What does the distinction mean? It implies that two things are not the same, hence duality exists there.
What is the Soul as different from the mind? The Soul is only a mental picture within the duality. Even if one says that he is immortal and exist eternally, only in duality he can say it i.e. the duality itSelf is mere illusion.
The illusion never reaches the Self, which is Soul, which is present in the form of the consciousness. The false Self never knows it. He who says he has a vision of the highest or describes it as super consciousness etc. does not understand consciousness, because it is free from all imaginations, because it exists prior to all experience and imagination.
Ordinarily knowledge arises from the experience of an object by a subject; that all knowledge of objects will only lead to more thinking but never gives one the ultimate reality.