n, see MN 52, SN 22:5, AN 4:124, AN 4:126, AN 5:28, and AN 9:36. It is sometimes argued that the first development of concentration is the only one that falls under the four jhṅnas, but the passages cited in these notes all show that jhṅna is involved in all four developments. The difference lies in how the practice of jhṅna is used. 5. Imperturbability is a quality of concentration that allows it to be used for the second and fourth developments of concentration (see MN 4). For more on imperturbable concentration, see MN 66 and MN 106. On an even higher level, the arahantâs mind is said to be imperturbable in the face of all sensory input. On this point, see AN 6:55. - --> - - - -