yat punaḥ pradīpamadhikṛtyaiva deśāntaravartinyās tat prabhāyā antarāvaraṇena vikārāpādanaṃ kriyate tan na tasyāḥ sākṣāt pradīpa upādānakāraṇam/
When, with reference to a lamp, a modification is brought about in its light extending to another place by [placing] an intervening screen, the lamp is not the direct material cause of that [light].