Brahma Knowledge, by L. D. Barnett, , at sacred-texts.com
§ 18. Organism of Soul.—I. Upanishads.—Every organic being is a soul, according to the Upanishads; and the degree of its organic development is directly proportioned to the merits of its former works. The highest therefore are the souls of gods and men. The soul in its human embodiment exercises three classes of functions: (1) the sense-organs (indriya), which in slumber or swoon become paralysed and merge themselves into (2) the organ of thought (manas), which converts the data of the sense-organs into conscious modes of thought and volition; and (3) the "breaths" (prāṇa), a term originally denoting all the functions of physical life, then those higher functions upon which generally depends all life, whether conscious or unconscious, and into which during sleep or swoon are merged the manas and the sense-organs already absorbed in the latter.
The name indriya for the sense-organs appears first in Kaṭh. and Kau. Other texts usually call them prāṇa (a collective term, from the supremacy of the prāṇa, or breath), and comprise under the
name ordinarily breath, speech, sight, hearing, and manas (e.g. B.A. I. iv. 7). The same ten indriyas as in the later system occur first in B.A. II. iv. 11, IV. v. 12, which adds manas and heart (cf. Pra. IV. 2). On manas as central function of cognition and action see B.A. I. v. 3, IV. i. 6, Ch. VII. iii f., Kaṭh. VI. 7. The sense-organs are compared to horses drawing the car of the body, manas to their bridle, Kaṭh. III. 3; in Maitr. II. 6 the organs of action are the horses, the organs of intelligence (see below) the reins, manas the driver. On the immersion of organs with manas in prāṇa see especially B.A. IV. iii. 12, Ch. VI. viii. 2, Pra. IV. 2 f. The "breaths" are usually given as five, viz.: (1) prāṇa in the strict sense, which in B.A. and Ch. denotes exspiration, and later exspiration and inspiration together; (2) apāna, in B.A. and Ch. the inspiration, later the wind causing digestion in the bowels or evacuation; (3) vyāna, respiratory action connecting prāṇa and apāna, variously conceived; (4) samāna, sometimes the wind digesting food, sometimes connection between exspiration and inspiration; (5) udāna, which carries food and drink up and down (Maitr. II. 6) and guides the soul to Brahma in death and sleep (Pra. III. 7, IV. 4).
II. Later Vedānta.—In the system of Śankara the gross body, subtle body (§ 19), karmāśraya (§ 20), and prāṇas are classed together as the "determinations" or upādhis by which the Self
conceives itself as an individual soul (above, § 12). Whereas the gross body is abandoned on death, the other organisms travel in a potential form with the soul throughout all its births. By the term prāṇa Śankara, following the old Upanishadic usage, designates not only the unconscious "breaths," but also the conscious indriyas. The indriyas (the functional forces whence arise the material sense-organs) according to him comprise the five functions of action (viz. speech, grasp, locomotion, generation, and excretion) and the five of buddhi or intelligence (viz. sight, hearing, taste, touch, and smell), with which is associated the manas as their centre. The prāṇas, or "breaths" in the strict sense are the five known in the Upanishads. Śankara explains prāṇa as exspiration, apāna as inspiration, vyāna as the force maintaining life when both exspiration and inspiration are checked, samāna as the digestive force, and udāna as the current leading the soul from the body on death (on II. iv. 8 f.). When death takes place, the indriyas sink into manas, this into the prāṇas, these into the individual soul (lodged in the heart), this into the "subtle body" (§ 19), which then starts on its wanderings. Thus Śankara (on IV. ii. 1 f.) explains the statement of Ch. VI. viii. 6 that on death Speech is merged in manas, this into prāṇa, this into Heat, this into the Higher Godhead. These words, he holds, mean that the potential functions of conscious sensation are
merged into those of unconscious vitality, the latter into the individual soul, this again into the "Heat," i.e. the "subtle body," which conveys the soul through its wanderings. See also §§ 12, 15.
The later Vedānta (e.g. the Vedānta-sāra and the Ātma-viveka and Vākya-sudhā ascribed to Śankara) schematises the functions of empiric thought by dividing the antaḥ-karaṇa, its collective organisation, into chitta, manas (often loosely called antaḥ-karaṇa), buddhi, and ahaṃ-kāra. To chitta it ascribes the function of passing notice, to manas that of deliberation, and to buddhi that of determination. Sometimes also it uses buddhi as a general term denoting both ahaṃ-kāra, the conception of egoity, which is the agent in empiric mental action, and manas, the instrument of egoity; in the false identification of these functions with the Self or Spirit lies the root of phenomenal illusion.