The Upanishads are love letters left behind so others as they come can find their way inside to the Divine. Attributed to the Indian mind, they were written by many hands spread far and wide. But the Truth contained within each is the same, for all Truth is One, though called by many names.
This is what you are doing now, you and the many others. You are doing the same. You have called My name. You have answered My call. And you have found Me, realized Me within, within yourself, within all. Thus you write what you know and your life as well shows.
Truth can not be kept down. Forever Truth lives. As you read these long ago writings you will see plainly the same Truth spoken again and again. Come home unto your heart. Come within. Some attribute this wisdom to oral tradition but Truth such as this is only known spiritually. Words do not serve the heart. Words are only a place to start.
The authors of the Upanishads were many, but they were not solely from the priestly caste. They were poets prone to flashes of spiritual wisdom, and their aim was to guide a few chosen pupils to the point of liberation, which they themselves had attained.
The term 'Upanishad' literally means, "sitting down near" or "sitting close to", and implies listening closely to the mystic doctrines of a guru or a spiritual teacher, who has cognized the fundamental truths of the universe.
In the Upanishads we get a glimpse into the workings of the minds of the great Indian thinkers who were unhampered by the tyranny of religious dogma, political authority, pressure of public opinion, seeking truth with single-minded devotion, rare in the history of thought.