_Om_ is the verbal symbol of Brahma signifying the Universal spirit ॐ ब्रह्मणि च । ब्रह्मणः नामबिशेषः तारानाथः so says the Katha Upanishad एतद्ध्येबाक्षरं ब्रह्म । This meaning is obtained from ॐ = om signifying _being_ or existence, and referring to the totality of existence expressed by the word Brahma (formed of बृह + मन) _universal pervasion_. [Sidenote: 5. Greatness of Brahma ब्रह्मत्वं बृहत्वञ्च ।] Om is used also to denote the vast magnitude of Brahma (ब्रह्मत्वं बाबृहत्वं) in the Maitrí Upanishad, which says “_Om_ is the greatness of Brahman, says one who continually meditates thereon.” (See Cowell’s Translation of Id. IV. 4. p. 253). This idea is naturally suggested by the infinity of the Universe pervaded and encompassed by the spirit of God. सर्ब्बं बिन्दु गतं ह्यैतत् ब्रह्माण्डञ्चापिकोटिशः । गायत्री तन्त्रं । The Ch’hándogya Upanishad speaks of the greatness and effects of _Om_ (I. 9). To this the scholium raises the question, what are its greatness and effects? Then answers it by saying;—“by the greatness of _Om_ is implied the existence of priests, the institutions of sacrifices &c. &c. Therefore is its greatness.” [Sidenote: 6. Om is the way to Brahma ब्रह्मज्ञानोपायः ।] “_Om_,” says the Mándukya Upanishad, “is the means (symbol) leading to Brahma,” as a hieroglyphic character to its significate. Here says the commentator Ánandagiri (p.336.) ओङ्कारो ब्रह्म वुद्ध्योपास्य मानो ब्रह्म प्रतिपत्युपायो भबतीति । आनन्दगिरि टीका । “It is known in all the Vedántas as the best means towards the accomplishment of one’s adoration.” (Ch’hándogya Upanishad p. 5 note.) [Sidenote: 7. Immutable & Imperishable ॐ अक्षरः ।] It is immutable, undecayable, imperishable, indestructible and immortal (अक्षरं). Thus in the Mándukya; ओमित्येतदक्षरमिदं बिकार रहितमित्यादि । The circle of O is considered the most perfect of all geometrical figures, as it was held by the Pythagoreans to be the best symbol to represent the perfections of the Supreme Being. It is the sign of divine immutability from the fact of every other figure changing its shape by its constant rotation round the centre and becoming a spheroid which is no more susceptible of change. Such is the changeable nature of all things until they become one with the Divinity. [Sidenote: Om Knowable. ज्ञेयं ।] _Om_ the symbol of God is said to be the knowable, because every part of its circumference is equidistant from the central observer. So is God said to be knowable (ज्ञेय) in Yoga philosophy for his knowableness to every one by means of meditation. Hence the Yoga system is called gnosticism contrary to the unknowableness of agnosticism. [Sidenote: 8. Eternity नित्यं ।] _Om_ is called eternal (नित्यं), because its circular form is the representation of eternity, having neither its beginning nor end (अनाद्यनन्तं): so it is the symbol of infinity, the circle being described by an infinite line. Thus Gaudapáda; अपूर्व्वोऽनन्तरोऽनन्तः नपरः प्रणबाब्यय । इति माण्डुक्य कारिकायां । १६ ।