Acharya Prashant explains that the mind always seeks an object or image to concentrate on, as the sense of being a subject depends entirely on the presence of an object. To think, the mind requires something with form, attributes, and characteristics. The Upanishads challenge this tendency by instructing one to concentrate on that which has no name, form, history, or limits. Since the mind cannot find any material to grasp, the thinker itself begins to dissolve. This is described as a method of Samadhi or a Zen-like practice where attempting to think about the unthinkable leads to the disappearance of the ego.