Wikipedia
Samatva ( Sanskrit: समत्व ) as an abstract noun means – equalableness, normal condition, state of indifference, equanimity, equality, equality with, uniform conduct towards. Its root is sama meaning – equal.
Samatva occupies a high place in the Bhagavad Gita. Sāmya, meaning – equal vision towards all human beings, is a variant of the word, Samatva, used in the Bhagavad Gita to mean – even-mindedness. Krishna in the context of metaphysical knowledge refers to equal-mindedness when he tells Arjuna that all feelings are transitory and fleeting, तांस्तितिक्षस्व therefore ignore them for they have to be endured (II.14) and that the wise are न व्यथयन्ति not tormented by these feelings (II.15). He once again refers to even-mindedness in the context of svadharma when Arjuna is told not to waver in the performance of his duty or shirk his duty, and to treat alike victory and defeat, gain and loss etc., for then he will not incur sin (II.31-38). Therefore, Arjuna is told –
योगस्थः कुरु कर्माणि सङ्ंग त्यक्त्वा धनञ्जय | सिद्ध्यसिद्ध्योः समो भूत्वा समत्वं योग उच्यते || "Perform your duty equipoised, O Arjuna, abandoning all attachment to success or failure. Such equanimity is called yoga." – Bhagavad Gita (II.48)This sloka delineates the process of practicing Karma yoga which is a part of human nature and promotes tranquility. Man reaches the ultimate state of unshakable stability through the constant practice of indifference to success and failure of actions. Action with selfish motive does not result in even-mindedness. In the context of Karma yoga, Krishna tells Arjuna that the sages, by virtue of true knowledge, see with equal vision all beings of all castes and creed because the Atman is present in all bodies without any distinction (V.18), and affirms that – इहैव तैर्जितः सर्गो येषां साम्ये स्थितं मनः that those whose minds are established in sameness and equanimity have already conquered the conditions of birth and death to be established in the Eternal (V.19). And, that –
आत्मौपम्येन सर्वत्र समंपश्यति योऽर्जुन | सुखं वा यदि वा दुःखं स योगी परमो मतः || "He is a perfect yogi who, by comparison to his own self, sees the true equality of all beings, in both, their happiness and their distress, O Arjuna." - Bhagavad Gita (VI.32)Then for that yogi there remains nothing in this world which has a separate identity from him, and no pain whatsoever; conscious of all such experiences but not affected by them he works for the uplift of others. Thus, Krishna harmonizes Śreyas (personal salvation) and Lokasamgraha (good of the society) by linking Śreyas with 'even-mindedness' and Lokasamgrah with 'equal vision'.
Swami Chinmayananda while commenting on Isha Upanishad (6), which speaks about the wise man beholding all beings in the Self, and the Self in all beings, gives the meaning of samatva as – the sameness of mind, inward tranquillity. The phrase 'All Beings' refers to the highest cosmic manifestation, and the phrase 'the Self in all beings' refers to Pure Consciousness, the inmost Atman of all embodied souls. The principle of Niśkāmakarma or the ideal of desire-less and motiveless action, does not bind the yogi to act’s consequences at the individual level; the yogi stays contented and even indifferent towards those very consequences; he knows that actions are not to be renounced, the fruits of actions alone are to be renounced. Once repulsion and action are removed what remains is "samatva".
The followers of Jainism consider the practice of samtava as Sādhanā because it is real human nature; they do not view samtava and dhyana as two varied aspects, according to them these two are interdependent, steadiness of the mind is reached by thinking about maitri (universal friendship), pramoda (emphasizing goodness), karuna (universal compassion) and madhyastha (indifference to sin of others). Mahavira had told Gautama that the nature of the soul is equanimity (Bhagavatisutra (9.386). Therefore, one who has samatva as his essential nature is called samayasāra.
In Gandhian aesthetics, samatva, understood as unity, equality, equanimity, balance and harmony in different perspectives, is the very essence of 'Sarvodya ideology'.