The instruments of knowledge are mind, intellect and cognitive and conative organs. Their association with the doer (Purusha) results in action, sensation and understanding.
The Purusha alone (soul in the absence of manas and indriyas) does neither initiate deeds nor enjoy the result of deeds. Combination of all these factors is responsible for the manifestation of every effect and without that nothing exists nor happens.
न ह्येको वर्तते भावो वर्तते नाप्यहेतुकः| शीघ्रगत्वात्स्वभावात्त्वभावो [४] न व्यतिवर्तते ||५८||
The Purusha, not alone but accompanied with manass and indriyas, is responsible for the manifestation of things. The process of decay on the other hand being too quick in succession does not need any cause as such.
Thus, the absolute soul is without a beginning or an end, but the Purusha (i.e. the combination of 24 elements) being caused by something is not so i.e. it has a beginning and is ephemeral. All that exists without cause is eternal. Anything produced from a cause is ephemeral.
तदेव भावादग्राह्यं नित्यत्व [१] न कुतश्चन| भावाज्ज्ञेयं तदव्यक्तमचिन्त्यं व्यक्तमन्यथा| |६०||
The absolute soul cannot be perceived by anything, for eternity is not caused by anything. So, the absolute soul is unmanifested and imperceptible. The manifested creation is, of course, otherwise.