One who knows both — knowledge and ignorance — together, crosses over death through ignorance and attains immortality through knowledge.

This verse offers the crucial synthesis, resolving the apparent contradiction of verse 9.

Vidyāṃ ca avidyāṃ ca yaḥ tat veda ubhayaṃ saha — one who knows both, knowledge and ignorance, together. The key word is saha — together, simultaneously. It is not first one then the other, but an integrated understanding.

Avidyayā mṛtyuṃ tīrtvā — having crossed death through avidyā. How can ignorance help cross death? Here avidyā is understood as karma, ritual action, dharma — the practices that purify, strengthen, and prepare the aspirant. Right action overcomes death in the sense that it creates conditions for knowledge.

Vidyayā amṛtam aśnute — attains immortality through vidyā. Direct knowledge of Brahman is what finally grants amṛta, immortality, liberation.

The teaching is practical: do not abandon action for meditation nor meditation for action. The householder who fulfills duties with awareness, the yogi who meditates without despising the world — both aspects are necessary.

This integration is the distinctive mark of the Īśopaniṣad and anticipates the Bhagavad Gītā’s synthesis between jñāna (knowledge) and karma (action).