The self illuminates itself without the medium of consciousness. It is said to be svayamprakāsa as opposed to jaḍa. In thick darkness you are not able to see the books and pencils placed on your table. The books and pencils do not shine forth for you; they do not manifest themselves to you.

The cit or self is ajaḍa or self-luminous

The self illuminates itself without the medium of consciousness. It is said to be svayamprakāsa as opposed to jaḍa. In thick darkness you are not able to see the books and pencils placed on your table. The books and pencils do not shine forth for you; they do not manifest themselves to you. If you bring a lamp, its light makes them appear to you. The books and pencils thus depend upon the light for their appearance. They are, therefore, objects depending on other things for our cognizing them. The lamp-light does not require any other light or any other object for our cognizing it. The lamp-light not only makes other objects such as books etc., manifest themselves to us, but, at the same time, it manifests itself to us without any medium. This analogy may, to a certain extent, help us to understand the expression svayaṁprakāsa or self-luminous object.  Only 'to a certain extent', for the analogy is not quite apt and is not on all fours, because, the lamp-light or, for that matter, any visible worldly object is not svayaṁprakāsa. Śāstras say that the self, the Supreme Being and the Divine world, aprākṛtaloka, are the only svayaṁprakāsa objects. Strictly speaking, even a lighted lamp does not possess illuminating quality, for its light does not make objects manifest themselves.

In every instance, it is our consciousness, jñāna that makes objects appear to us. In spite of the presence of the lamp-light, the objects will not appear to us in the absence of jñāna or consciousness. Even the senses do not illumine objects. The senses only cause the origination of consciousness. The function of the brilliant light, such as that of an electric lamp, is only to help the senses which originate consciousness, by removing the obstacle for such origination, namely, darkness. In ordinary parlance, we say that a lamp illumines objects having regard to the help rendered to the organ of sight in the production of consciousness. Merely because the light removes the obstacle for the origination of consciousness, it cannot be said to illumine the object. That, which is really conducive to vyavahāra or talk, does illumine objects, and that is, jñāna or consciousness. Therefore, consciousness alone illumines objects. Mere light does not illumine objects. Therefore, light is not, strictly speaking, luminous; and much less, is it self-luminous. We shall deal with the attribute-consciousness at length later on. The self does not require even this attribute consciousness for its illumination. It illumines itself. Therefore, the self is said to be self-luminous. The upaniṣad says: “The puruṣa or self is self-luminous”.

अत्रायंपुरुषःस्वयंज्योतिः । - Br. Up.

We have already seen that the existence of the self is self-evident even in deep sleep.