Katha-1-3-10-indriyebhyaḥ

Sri Shankara’s Commentary (Bhashya) translated by S. Sitarama Sastri

Now this subsequent portion is introduced for the purpose of showing that the goal to be reached should be understood to be the Pratyak (the internal) âtman, the subtlest proceeding from the gross senses in the ascending degree of subtlety. The senses are gross and those rudiments (Vishaya) from which these spring for their own illumination are subtler than the senses, their own effects, greater than these and the âtman of these, i.e., bound up with these; subtler than these rudiments and greater than these, being the âtman of these, is the mind. Here, by the word mind is denoted the rudiments of the Bhûta (Bhûta Sûkshma) from which mind originates. Than the mind which is the origin of volition, deliberation and the rest, the intellect is subtler, greater, and more possessed of the functions of seeing, hearing, etc., does not shine, as the âtman of any being concealed by ignorance and delusion. Oh, how deep, unfathomable and marvellous this Mâya, that every living being, though really in its nature the Brahman, does not, though instructed, grasp the truth ‘I am the Paramâtman’ and feels convinced, without any instruction that he is such a person’s son mistaking for the âtman the combination of the body, and the senses, etc., which is not the âtman and is only perceived by him, like the pot, etc.; indeed, the world wanders repeatedly deluded by the Mâya of the Brahman alone; so the smriti also says ‘Being concealed by Yôgamâya, I do not shine to all, etc.’ Are not these statements inconsistent? Knowing him, the intelligent do not grieve and ‘he does not shine.’ It is not so. It is said he does not shine, because he cannot be known by the unpurified intellect; but he is seen by the purified intellect. Agryayâ, like a point, i.e., concentrated, subtle, i.e., capable of perceiving subtle objects. By whom? By the subtle seers, i.e., by persons, who, by seeing the different degrees of subtlety as pointed out by the rudiments, are subtler than the senses, etc., are characteristically able to see the subtlest, i.e., by learned persons.

Links
Various resources on the Kathopanishad
Upanishad Series – Katopanishad Commentary by Swami Chinmayananda