मन्त्राणामचिन्त्यशक्तिता
mantrāṇāmacintyaśaktitā
"The power of the mantra is unthinkable."
-Paraśurāma Kalpasūtra 1.8
Though the meaning of the mantra is ascertainable by the mind and can be dwelt upon by the concentrated thought of the mind, its power is beyond the range of the mind to measure. That is because the power is not derived from a mental origin. It proceeds from a deeper and higher plane of existence from where the mind falls back. And there are other factors too which add to the effectivity of the mantra."
-M.P. Pandit
in "Bases of Tantra Sadhana"
DIPTI Publications Sri Aurobindo Ashram
1972.