The idea itself sounds absurd, we see and perceive the universe, we know it has to exist. But, does it really? What proof do we have that our senses are not deceiving us? After all, our senses and perception are all based on electric impulses. What is to stop these impulses to be designed in such a manner so as to create a make believe universe in our minds? What if the reality that we see is only for us? In other words, what proof do we have that we are not stuck in a matrix-like situation (like in the movie) where our senses have been deceived into believing in a non-existant universe? Is this universe only an illusion? Is there no way we can realize the truth?
Let us assume this universe is an illusion, and we somehow manage to pull the plug on the illusion. What guarantee do we have that the ensuing reality is not another layer of illusion? This can keep going on forever like the chicken or the egg question. The more you think about this, the more you realize that our senses are not as dependable as we thought when we seek the truth.
Take this a step further. I look down and see my fingers and toes. I can move and feel them. But since my senses cannot be depended upon, do my fingers and toes exist? Does my body exist? Do I exist outside of the mind? Does the mind itself exist?
There has to be something deeper, something more subtle than our gross senses and our mind. It is our Atman, loosely (and somewhat inaccurately) translated as soul. We have to transcend this material universe, which is nothing but an illusion to realise our true self. Our mind can only help us in going so far, but beyond a certain stage, we have to transcend the mind itself.