Verses on Sāṃkhya 45

He states the defining characteristic of the intellect:

Intellect is ascertainment; virtue, knowledge, dispassion, and lordly power
Are its sattvic form; the tamasic [form] is the opposite of this. // 23

"Ascertainment," and so forth. With respect to sense objects such as sound, this is the ascertainment: "This is sound," down to "This is smell." [Such is] the definition of the intellect. And it has eight forms.

[With the words] 'virtue, knowledge, non-attachment, mastery': among these, that ascertainment which consists in practice regarding proper conduct is virtue. There are five restraints and five observances. As it is stated in the exposition of Sāṃkhya: 'Non-violence, truthfulness, non-stealing, celibacy, and non-possession are the restraints'; 'Purity, contentment, austerity, self-study, and devotion to God are the observances.' Among these, contentment is the absence of desire to acquire more than the immediate means near at hand. Austerity is the conquest over hunger, thirst, cold, heat, postures, and instruments; the silence of a log and the silence of an ascetic; and vows such as the kṛcchra and the cāndrāyaṇa. Self-study is the study of the scriptures on liberation, or the repetition of the syllable Om. Devotion to God is the worship of an exalted deity, because [their] conduct is like that of those who are not subject to the cycle of rebirth. Practice contrary to that is vice.
Knowledge is the ascertainment of the individual names, characteristics, and purposes of the twenty-five principles, [namely,] the knowledge of the distinction between the constituents and spirit. The rest is ignorance.
Non-attachment is turning away from sense objects, the body, and the organs due to seeing their defects. Attachment is desire for them.
Mastery is eightfold: atomicity, magnitude, lightness, reach, freedom of will, lordship, control, and fulfillment of desires at will. Among these, atomicity is minuteness, by which quality one wanders about having become subtle; it is called atomicity because the cause is metaphorically applied to the effect. The same should be applied in the subsequent cases. Lightness is levity, by which one becomes lighter than the wind. Magnitude is greatness, by which [one expands] throughout the worlds. Reach is virtue and the rest, by which quality there is obtaining of whatever is desired. Freedom of will is abundant volition, by which one becomes many or many become one at will. Lordship is sovereignty, by which immobile and other entities obey one's command. Control is mastery, by which one moves independently. Fulfillment of desires at will: one whose nature is to abide according to desire, that is, volition, is one who abides wherever desired; its state is fulfillment of desires at will. Because verbal roots have multiple meanings, [the root] śī- stands for remaining: the meaning is, by which quality there is abiding in the sky, mid-region, or on the earth.
[With the words] 'this form is sattva-dominated': because of the abundance of the sattva and tamas constituents; the meaning is that when the sattva constituent of the intellect is predominant, then these four arise.
[With the words] 'the tamas-dominated is the reverse of this': the meaning is that when the tamas constituent is aroused, the opposite of the four beginning with virtue, which are characterized by predominance [of sattva], arises: vice, ignorance, non-vairāgya, and non-mastery. // 23