Mandukya Karika, verse 4.40

Text

नास्त्यसद्धेतुकमसत् सदसद्धेतुकं तथा ।
सच्च सद्धेतुकं नास्ति सद्धेतुकमसत्कुतः ॥ ४० ॥

nāstyasaddhetukamasat sadasaddhetukaṃ tathā |
sacca saddhetukaṃ nāsti saddhetukamasatkutaḥ || 40 ||

40. The unreal cannot have the unreal as its cause, nor can the real be produced from the unreal. The real cannot be the cause of the real. And it is much more impossible for the real to be the cause of the unreal.

Shankara Bhashya (commentary)

From the standpoint of the Ultimate Reality, things can, in no way, enter into causal relation. How? An unreal cannot be the cause of another unreal. An1 unreal entity such as the horns of a hare, which may be said to be the cause of another unreal entity such as a castle in the air, has no existence whatsoever. Similarly,1 an object like a jar, which is perceived and which is the effect of an unreal object like the horns of the hare, is never existent. In3 like manner, a jar which is perceived and which is the effect of another jar that also is perceived to exist, is, in itself, non-existent. And4 lastly, how is existence possible of a real object as the cause of an unreal one? No other causal relation is possible nor can be conceived of. Hence men of knowledge find that the causal relation between any objects whatsoever is not capable of being proved. The causal relation between the waking and the dream states has been stated from the empirical standpoint alone. But it cannot be established from the standpoint of Truth. Further, no causal relation, whatsoever, is admissible.