Avatarika
तत्र प्राणा वै सत्यमित्युक्तम् ।याः प्राणानामुपनिषदः,ताः ब्रह्मोपनिषत्प्रसङ्गेन व्याख्याताः- एते ते प्राणा इतिच ।ते किमात्मकाः कथं वा तेषां सत्यत्वमिति च वक्तव्य-मिति पञ्चभूतानां सत्यानां कार्यकारणात्मकानां स्वरूपाव-धारणार्थम् इदं ब्राह्मणमारभ्यते-
In plain words
We have already said that the breaths are the real. Their mystic identification was explained earlier, in the course of discussing the teaching about Brahman — 'these very breaths are those' — and that much is settled. But what are they actually made of, and how do we know their reality holds up? That still needs saying. So, to pin down exactly what the five elements are — real things, each both cause and effect at once — this section now begins.
Close to the Sanskrit
There, it has been said that the breaths, indeed, are the real. The mystic teachings of the breaths, which were explained in connection with the topic of the Brahman-teaching — 'these are those very breaths' — thus too. Of what nature are they, or how is their reality to be established? — this still needs to be said. Thus, for the purpose of ascertaining the true nature of the five elements, which are real and consist of cause and effect, this section is begun.