Bramha vidya as taught by Keno upanishad.

Yasya amanth thasya manth manth yasya na ved sa |

Meaning:To that person for whom Brahman is unknown , Brahman is truly known. To that person who considers that he knows The Supreme spirit [ just like the things he knows many things in creation] that person doesn't in fact know.

Commentary:

That is -a person who truly knows Brahman ,knows that he cannot be known through senses or mind.And the person who thinks he knows him is actually having a concept of Brahman. A concept of Brahman is not like realising the true nature of Brahman.

The above Sloka brings out the limitations of human intellect and knowledge to comprehend the Supreme being.

Sloka.Prathi vodhi vindhitam matham amirthvam hee vindhate|

This is the most profound Sloka in this Upanishad.

simply stated--All beings are like electric lamps that glow by the power that is received from the Supreme being, themselves not knowing, it!

Reason, in respect of trying to comprehend the ultimate reality is like the impossible conception of a sleeping man trying to know what he is about ,without waking up!

Sloka:Atmana vindhate veerya vidhya vindhate mritam.

Meaning:Self discipline gives strength of spirit . To one so strengthened there is awakening and the knowledge --that is, the intuitive understanding that Brahman is and is in everything, bestows immortality!