Having provided an overview of the higher and the lower knowledge, the Mundaka Upanishad next takes up the actions of the seeker. Chapter 1, Section 2, verse 1, as translated by Sri Aurobindo:
“This is That, the Truth of things: works which the sages beheld in the Mantras (The inspired verses of the Veda) were in the Treta (The second of the four ages) manifoldly extended. Works do ye perform religiously with one passion for the Truth; this is your road to the heaven of good deeds.”
Every action has consequences. “Works” are karma, and they create a chain of cause and effect. Action undertaken with a focus on attaining the Truth of existence will lead eventually to “the heaven of good deeds”. Some interpret this literally and expect to go to a physical location of heaven. Yet this can be a psychological space of happy and positive energy and feelings that result from positive actions. Modern day western scientists are now positing that there are multiple dimensions in what is known as “string theory” that occupy the same space. These dimensions provide answers to questions of quantum physics and may help us understand that someone living in our physical world, may actually be occupying another dimension of existence based on the heavens or hells of our own creation through the motive and focus of our actions. While we may believe in the existence of physical locations of heaven or hell, we may also recognize that we create our own subjective heaven, or our own subjective hell, based on how we approach the meaning, purpose and directed actions of our lives in the physical world we occupy. As with any result, however, they only last as long as the impetus in that direction continues, and then, as the energy decays, the results take on a new character.
There are stories in the ancient texts that speak of someone who undertakes sacrifices, chants powerful mantras, and builds up a powerful body of good deeds. This individual attains a “heaven” as a result of this focus and these actions, but eventually, as the person enjoys the “heaven” the actions themselves slack off, and thus, eventually, the sojourn in that heaven is ended and they go back to a world of suffering. Some hold that such heavens are not evolutionary as they encourage enjoyment rather than continued effort, and thus, they even claim that the gods who occupy various heavens have to take human birth in order to progress in the evolutionary development.
Focus on the Truth, and continued good deeds, helps to calm and concentrate the mind, and thereby remains a preparatory step towards higher realisations and development of higher evolutionary states of awareness, as long as the seeker does not rest content in the achievement of some heavenly experience and discontinue further efforts.
Sri Aurobindo, The Upanishads, Mundaka Upanishad, pp. 193-210