Sri Aurobindo translates Katha Upanishad, Second Cycle: Third Chapter, Verses 6-8: “The calm soul having comprehended the separateness of the senses and the rising of them and their setting and their separate emergence, puts from him pain and sorrow. The mind is higher than the senses, and higher than the mind is the genius, and above the genius is the Mighty Spirit, and higher than the Mighty One is the Unmanifested. But highest above the Unmanifested is the Purusha who pervades all and alone has no sign nor feature. Mortal man knowing Him is released into immortality.”
A number of Upanishads make the points raised here, albeit with slightly different wording. The senses constantly send impulses to the brain for processing and attention. For most people, this means they are constantly reacting to outer things and external events. Their minds are turned outwards based on attending to the senses. The “calm soul”, the individual who is centered within, does not allow the senses to dominate his perception of existence. There are numerous methods for bringing about the change from sense-dominated to inner-centered awareness, which are discussed in the spiritual and psycho-spiritual literature from all around the world. Patanjali discussed this issue at length in his Yoga Sutras. Swami Vivekananda in his lectures on Raja Yoga delved deeply into this issue. Once the linkage between the outer sense impressions and the calm mind has been dissolved, the impressions no longer have the power to create “pain and sorrow”.
The second verse here sets forth a hierarchy of awareness. People will generally agree that the mind is higher than the senses, as it incorporates all of the input from the senses, which after all, are not independent actors nor decision-making elements, while it coordinates, analyzes, categorizes and responds. Where the Upanishad goes beyond the mind, however, we are dealing with experiential levels that many people have not consciously experienced, or if experienced, understood. This is where the Upanishads provide real insight into levels of consciousness that represent the internal shift from the ego-centered individual relying on the mind and the senses, to the divine-based awareness that transcends the ego-consciousness.
The first step beyond is what Sri Aurobindo translates as “the genius”. This is a translation of the terminology “sattvam uttamam”, which could also be literally translated as supreme clarity or light. Other Upanishads use terminology such as “vijnana” for this next stage of awareness, which generally can be translated to mean, “Knowledge Consciousness” or Reasoning Intelligence. Beyond this stage is the “Mighty Spirit” which is a translation of the term “mahat” . In this case, the awareness goes beyond the individual to a wide, and vast consciousness that encompasses the universal creation, and in which, when the attention is turned in a particular direction, anything can be known, not through sense perception or analytical function of the mind, but directly. Beyond this stage is the “Unmanifest” the Akshara Purusha, which is the goal of those who renounce all commerce with the life of the world and the action of the senses. Beyond this is the Supreme Purusha, which the Bhagavad Gita calls the “Purushottama”, which encompasses both the unmanifest and the manifest within its one, omnipresent, reality.
Sri Aurobindo, The Upanishads, Katha Upanishad, pp. 213-241, and Kapali Sastry, Lights on the Upanishads, pp. 104-129