In plain words
Sva-prayojana. What is svaprayojana? It is putting things to use for this personal self! So all the work man does today is self-seeking; none of it is for the good of others. The Buddhi in humanness is bound up with self-interest and self-gain. What is free of self-interest and self-gain is tāraka. What is bound up with self-interest and self-gain is māraka. We must understand well the difference between this tāraka and māraka. All actions done with the feeling of the Ātma belong to tāraka! All actions that are physical, worldly, done as one's lot brings them, are māraka! What is tāraka?
Never letting awareness slip into forgetting, always, in waking, dream and deep sleep, without reserve, at all times, constantly, the jīvātma recites the tāraka: you must know its aim, brother; by the grace of the Sadguru, search out the difference and see it, brother!
Tāraka is what is beyond waking, dream and deep sleep. That is why they called it ‘Turīya’. That is the true tāraka. The true Buddhi is what has attained that principle of tāraka.
The true principle of the Buddhi is the form of mind, word and body
In olden days some Brāhmins devoted to their observances would, at mealtime, recite the mantra ‘Annaṃ brahma, rasaḥ viṣṇuḥ bhoktā devo maheśvaraḥ’ and only then begin to eat. What does it mean? ‘May the food I have eaten spread through the whole body as its essence and give me strength! To use this strength well, may a good mind be granted to me! May my speech be purified!’ That is the meaning of this mantra. This food and this essence, all of these, are the form of Brahmā, Viṣṇu and Maheśvara. So the food we eat gives strength to the gross body. It turns into the subtle mind.