The meaning of this passage by Bodhisattva Nāgārjuna is that dharmas do not give birth to themselves, nor are they born from other things. That is to say, one thing does not give birth to another thing; dharmas are also not born from the mutual combination of themselves and other conditions, nor are they born without a cause for their arising. The meaning of the last line is that the arising of dharmas has a cause; they cannot arise without a cause.
Then what is the cause? The fundamental cause is the true mind, the tathāgatagarbha. All dharmas come from the mind-substance of the tathāgatagarbha, which stores the seeds; they are not created by any deity or by God. The true cause of all dharmas is the tathāgatagarbha, and the source is the tathāgatagarbha. Therefore, dharmas are subject to arising; whatever arises also ceases. Although they arise, there is no true arising—they are all illusory, conjured up by delusion. Though born, they are not born; they are merely false appearances.
The only dharma that is truly unborn is the tathāgatagarbha. He was not born; He has existed from the very beginning. He is beginningless, and therefore also endless. What has a beginning has an end; only the beginningless is endless.
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