... through the medium of the empowered mantra, the power that resides in the Heart provides the possiblity of a return to Shiva, which is to say, the possiblitiy of enlightenment...
Abhinavagupta identifies the Goddess in the Heart with the Supreme Word (para-vak)... This Supreme Word, while ultimately beyond any of the combinations of human speech, may be transcribed on the gross level by one of serveral mantra-s.. The fragmented and restless mind is thus calmed, awakened, and intensified by the mantra, which, tending automatically to move to its own source, discovers the fullness and unboundedness of the Heart. There the disciple will hear the Supreme Word as the unstruck (anahata) sound of the Heart which is the universal life force or cosmic breath.
(p. 83)
{The mantra} constitutes the sound-form of the Goddess, who then enters the boundaries of the {spiritual aspirant's} finite mind and begins to work a process of expansion that will lead to the full manifestation of shaktipata {i.e. grace}.
(p. 168)
Initiation {of the spiritual aspirant by the guru} is not the transmission of any specific fact or technique. It is rather the transmission of the infinite Self. More precisely, it is the process by which the initiate gains access to a true knowledge of the Self he already is. By means of initiation, the {spiritual aspirant} is opened to the nirvikalpa condition of immediate perception of the unboundedness of Shiva. There is a sense in which he is "infected" with the germ of infinity, with the "seed", which will sprout into the acquisition of the state of enlightenment. This seed, which will ultimately grant him the freedom and spontaneity of an embodied Shiva, is transmitted to him in the highly charged and compressed form of the mantra.
(p. 170)
... the mantra is said to be essentially composed of the force and power of consciousness... When Abhinavagupta states that liberation is achieved as soon as the mantra is received, his initial meaning is that the eventual attainment of liberation is assured. In addition, he also means that once the practitioner has truly come to pronounce {and} to remember the mantra, this attainment will coincide, in effect, with the attainment of liberation. The true attainment of the mantra in this sense means that acquisition of the very force and power of consciousness itself. Thus, in the {spiritual practice} presented in the Paratrishika-laghuvritti, method and goal eventually coincide because the essence of the mantra is identical with the goal of the tantric path.
(pp. 163-164)
In terms of the mantra, the process involves harnessing the power that resides in consciousness and allowing the finite mind to vibrate more quickly, to expand and to reach the fast vibration that characterizes the state of Bhairava. The attainment of this state is synonymous with the condition of jivan-mukti.
(p. 174)
Editor's note: Since the initiation of a disciple by a guru involves the transmission of a mantra, more information on mantras can be found under the topic: The teacher.