That eternal entity is agitationless, so it is not moved by the three-fold urge. It does not order the senses about for this purpose or that. The question then arises: Do the mind (manas), the vital air (prana), speech, the eye, the ear, etc., carry out their respective functions prompted by the law of cause and effect? Or are they moved by the wish of a conscious force? That is the doubt.
The ear has the capacity to know sound, the eye is endowed with the skill to know and distinguish form. The other senses are also similarly equipped. When the mind passes out through the knowing-senses toward objects and envelops them, you acquire knowledge about them. Therefore, the five senses and the mind are all instru- ments of knowledge. How could they manage to perform this intelligent function, being themselves devoid of intelligence?
Well, the answer is: It is all due to the presence of the Atma, due to the reflection of the effulgence of the Atma on the inner instrument of mind, intellect, memory, and ego (an-thah-karana). The Sun illumines the world and makes it active in a thousand ways. So too, the Atma, by its spiritual power (tejas), activates and illumines the world. All instruments of knowledge are activated by the Atma.
The electric current energises a machine and does various operations —printing, etc.— but it is not visible or concrete. The electric current is the mover of the movement, the machine of the machine. So too, the Atmic splendour (tejas) is the Ear of the ear, the Eye of the eye. That is the activating current.
The wonder is: the Atma is inactive and without qualifications. It does not get anything done with the mind or the senses, remember. They get activated by the very presence of the Atma! The rays of the Sun are not at all aware of the activity they invoke; the Atma is not responsible for the activity of the senses.
(This teaching was given by Varuna to his son, Bhrigu.)