Homage to The Mother of All Wisdom! 

Thus have I heard: 

At one time the Lord dwelt at Rajagrha, on the Vulture Peak, together with a large congregation of renunciates and with countless bodhisattvas. At that time the Lord addressed Venerable Ananda:

“Ananda, do receive, for the sake of the welfare and happiness of all sentient existence, this perfection of wisdom in one letter, the letter A.”

Thus spoke the Lord. The Venerable Ananda, the large congregation of renunciates, the assembly of bodhisattvas, and the whole world with its devas, humans, asuras, and heavenly musicians rejoiced at the teaching of the Lord.

~ Prajnaparamita Ekakshari Sutra

The letter 'A' is the essence of all mantras, and from it there issue forth everywhere immeasurable mantras; All frivolous arguments cease, and it is able to produce skillful wisdom.

"Lord of Mysteries, why is this the essence of all mantras?" 

The Buddha, honored among two-legged beings, has taught that the letter 'A' is called the seed. Therefore, everything is like this, [generated and born from this seed,] and it rests in all the limbs; Having allocated it as appropriate, bestow it everywhere in accordance with the rules. Because that primordial letter 'A' pervades the augmented letters, the letters form sounds, and the limbs arise from this. 

~ Vairocanābhisaṃbodhi Sutra

The 'A' is inherent in the letter 'H'. The sound 'A' is the mother of all letters; it is the essence of all sounds; and it stands for the fountainhead of all-inclusive Reality. “The very act itself of opening the mouth in order to utter any sound is accompanied by the sound 'A'; therefore, apart from the sound 'A', no sounds are possible. The sound 'A' is the mother of all sounds.” If we see the letter 'A', we know that all things are empty and nil [i.e. only perceptually separated, but united with the formless totality of an eternally standing vibration]. This is the invariant meaning of the letter 'A'.

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Three ultimate meanings of the letter 'A' can be identified: 1) being, 2) empty, and 3) uncreated. The letter 'A' in the Sanskrit alphabet represents the first sound. If it is the first [among letters, therefore], it is relative. We therefore define it as “being.” 'A' also has the meaning of non-arising. If anything arises in dependence, it does not have its own independent nature. We therefore define it as “empty.” By “uncreated” is meant the Realm which is one and real, that is, the Middle Way. Nāgārjuna said: “Phenomena are empty, temporal, and also middle.”  …this single letter is the mantra of Mahāvairocana. A sūtra states: “The letter 'A' signifies ‘the enlightened mind,’ ‘the gateway to all teachings,’ ‘nonduality,’ ‘the goal of all existences,’ ‘the nature of all existences,’ ‘freedom,’ and ‘the Dharmakāya.’” These are the ultimate meanings of the letter...

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Those who understand the meanings of the letter 'A' are to meditate on it resolutely; they should meditate on the perfect, luminous, and Pure Consciousness. Those who have had a glimpse of it are called those who have perceived the absolute truth. Those who perceive it all the time enter the first stage of Bodhisattvahood. If they gradually increase their competence in this meditation, they will finally be able to magnify it until its circumference encompasses the entire universe and its magnitude becomes as inclusive as space. Being able freely to magnify or to reduce it, they will surely come to be in possession of the all-inclusive wisdom. The student of the yoga should devote himself to the mastery of the Three Mysteries and the Five Series of Meditation. The Three Mysteries are: the mystery of body – to make mudrās and to invoke the presence of the sacred object of meditation; the mystery of speech – to recite the mantras in secret, pronouncing them distinctly without making the slightest error; the mystery of mind – to be absorbed in yoga, keeping one’s mind in a wholesome state like that of the bright, pure and full moon, and to meditate on the enlightened Mind. 

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In the minds of all sentient beings there is an element of pure nature… It is likened to one of the sixteen phases of the moon – that in which the moon appears brightest… Therefore, a mantra practitioner should, by means of the syllable visualization, awaken the inherent brightness within his mind, causing a gradual cleansing and brightening, and a realization of the knowledge of the non-arising of phenomena. The 'A' syllable has the meaning of the originally non-arisen nature of all dharmas [i.e. phenomena, the means of understanding them and the true ways of living among such things].

~ Meaning of the Word Hum & Bodhicitta-śāstra, by Kobo Daishi

Because its essence is empty, it is free from the limit of eternalism. Because its nature is luminous, it is free from the extreme of nihilism. Because its compassion is unobstructed, it is the ground of the manifold manifestations.

~ Aspirational prayer for the Ground, Path and Result

~ Πύρρων ὁ Ἠλεῖος…
αὐτὸς μὲν οὐδὲν ἐν γραφῇ καταλέλοιπεν, ὁ δὲ γε μαθητὴς αὐτοῦ Τίμων φησὶ ~

δεῖν τὸν μέλλοντα εὐδαιμονήσειν εἰς τρία ταῦτα βλέπειν· πρῶτον μέν, ὁποῖα πέφυκε τὰ πράγματα· δεύτερον δέ, τίνα χρὴ τρόπον ἡμᾶς πρὸς αὐτὰ διακεῖσθαι· τελευταῖον δέ, τί περιέσται τοῖς οὕτως ἔχουσιν. τὰ μὲν οὖν πράγματα φησὶν αὐτὸν ἀποφαίνειν ἐπ᾽ ἴσης ἀδιάφορα καὶ ἀσταθμῆτα καὶ ἀνεπίκριτα, διὰ τοῦτο μήτε ταῖς αἰσθήσεσιν ἡμῶν μήτε ταῖς δόξαις ἀληθεύειν ἢ ψεύδεσθαι, διὰ τοῦτο οὐδὲν μὴ πιστεύειν χρῆναι, ἀλλ᾽ ἀδοξάστους εἶναι καὶ ἀκλινεῖς καὶ ἀκραδάντους εἶναι, περὶ ἕκαστον λέγοντας 

ὅτι, οὐ μᾶλλον τοῦτο, ἢ οὐχὶ τοῦτό ἐστιν, ἢ καὶ οὐ μᾶλλον τοῦτο, ἢ οὐδὲν ἐστιν.

τοὺς μέντοι γε διακειμένους οὕτως ἐπιφέρει Τίμων φησὶν εὐδαιμονῆσαι.

~ Pyrrho of Elis… left nothing in writing himself, but his student Timon says ~

The person who intends to be happy must consider three things: First, what the nature of things is; Second, in what way we should relate to them; And third, what will result for those who so relate to them. Now, he says that things are by nature equally indifferent, unstable, and indeterminate... Because of this, neither our perceptions nor our beliefs are truth or lie; Therefore, one ought not to put trust in them, but be without beliefs, Inclined toward nothing, and unwavering, Saying, concerning each thing: 

This is, no more than it is not, or both is and is not, or neither is, nor is not.

Nevertheless, Timon adds that those who are so disposed will be happy.

~  Aristocles' Fragment of Timon's Pytho