Just as a spider weaves its net from the materials of its own body, so does Ishwara create this universe out of Himself.
The ego identifies himself with casual bodies undergoes various sufferings and strives for liberation.
One may be indifferent to the enjoyments of this world only in expectation of better enjoyments in the next. This kind of indifference is tainted with desires, which bar the door to knowledge. But the indifference that results from a due deliberation on the evanescent nature of this world as well as the world to come, is alone pure and productive of the highest good.
In this ever-changing world there is one changeless being as witness of these changes. This permanent ever-seeing being is Atman.