Now "concentration" [_yoga_] consists [by i. 2] in "the suppression of the modifications of the thinking principle," which stops the operation of the "afflictions," &c.; and this "suppression" is not considered to be merely the non-existence of the modifications [_i.e._, a mere negation], because, if it were a mere negation, it could not produce positive impressions on the mind; but it is rather the site of this non-existence,[426]--a particular state of the thinking principle, called by the four names [which will be fully described hereafter], _madhumatí_, _madhupratíká_, _viśoká_, and _saṃskáraśeshatá_. The word _nirodha_ thus corresponds to its etymological explanation as "that in which the modifications of the thinking principle, right notion, misconception, &c., are suppressed (_nirudhyante_). This suppression of the modifications is produced by "exercise" and "dispassion" [i. 12]. "Exercise is the repeated effort that the internal organ shall remain in its proper state" [i. 13]. This "remaining in its proper state" is a particular kind of development, whereby the thinking principle remains in its natural state, unaffected by those modifications which at different times assume the form of revealing, energising, and controlling.[427] "Exercise" is an effort directed to this, an endeavour again and again to reduce the internal organ to such a condition. The locative case, _sthitau_, in the aphorism is intended to express the object or aim, as in the well-known phrase, "He kills the elephant for its skin."[428] "Dispassion is the consciousness of having overcome desire in him who thirsts after neither the objects that are seen nor those that are heard of in revelation" [i. 15]. "Dispassion" is thus the reflection, "These objects are subject to me, not I to them," in one who feels no interest in the things of this world or the next, from perceiving the imperfections attached to them. Now, in order to reduce the "afflictions" which hinder meditation and to attain meditation, the _yogin_ must first direct his attention to practical concentration, and "exercise" and "dispassion" are of especial use in its attainment. This has been said by Kṛishṇa in the Bhagavad Gítá [vi. 3]-- "Action is the means to the sage who wishes to rise to _yoga_; But to him who has risen to it, tranquillity is said to be the means." Patañjali has thus defined the practical _yoga_: "Practical concentration is mortification, recitation of texts, and resignation to the Lord" [ii. 1]. Yájñavalkya has described "mortification"-- "By the way prescribed in sacred rule, by the difficult chándráyaṇa fast, &c., "Thus to dry up the body they call the highest of all mortifications."[429]