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"The senses wander, and the mind follows them, just as the wind carries a boat. When the mind is free to roam, it takes the intellect along with it."
"Therefore, the soul does not shine brightly in a restless mind. It is observed that just as a mirror possesses the power to reflect, but when it becomes tarnished, it cannot reflect any object, similarly, the unstable mind, which runs after external objects, does not perceive the soul, not because of any obstacle, but simply due to its own weakness."
"Thus, it is proven that the mind, senses, microscopes, and all other instruments, being material, do not have the power to negate the soul."
"(3) Proof of Existence from Negation - Some people argue that we cannot be certain about the soul, but only experience its absence at times, because sometimes thoughts arise in the mind like 'I am not' etc. However, they should understand that this very thought proves the existence of the soul, because how can such a thought arise if there is no soul? The one who is negating is the soul itself. Shankaracharya has stated this in his commentary on the Brahma Sutras: 'The one who negates is indeed the self, its own nature.' (2.3.137)"
"(4) Logic - This also supports the independent existence of the soul. It states that in the world, every object has an opposite. For example, darkness has light as its opposite, heat has cold, and pleasure has pain. Similarly, there must be a conscious entity that is the opposite of inert matter."