Samatha-vipassanā: 'tranquillity and insight', are identical with concentration samādhi see: understanding paññā, and form the two branches of mental development bhāvanā. 1 'Tranquillity' is all unperturbed, peaceful and lucid state of mind attained by strong mental concentration. Though as a distinct way of practice see: samatha-yānika, it aims at the attainment of the meditative absorptions jhāna, a high degree of tranquil concentration though not necessarily that of the absorptions is indispensable for insight too. Tranquillity frees the mind from impurities and inner obstacles, and gives it greater penetrative strength.