The Second Jhāna
DN 22 Mahāsatipaṭṭhāna Sutta gives the standard formula for the second jhāna as follows:
With the stilling of directed thought and evaluation he enters and remains in the second jhāna, which has internal serene-clarity and unification of mind free from thought and evaluation, and has joy and pleasure born of composure.
With the elimination of directed thought and evaluation in the second jhāna, the two factors of serene-clarity (sampasādana) and mental unification (cetaso ekodibhāva) become prominent enough to be experientially distinguished. Just as the joy and pleasure born of seclusion and the concomitant expansive mind (mahaggatā citta) of the first jhāna opens up a whole new vista of experience not previously available, and display the limitations of conventional sensory cognition, now the serene-clarity and mental unification experienced by the silent mind in the second jhāna reveal another new level of meditative composure.
Here the experience of the silent mind can be likened to the surface of a completely tranquil lake. This is serene-clarity and mental unification. With this experience there is a definite sense of confidence in the quality of this internally composed level of samādhi, along with the subtle joy and pleasure thereby experienced, which DN 9 designates as an actual refined recognition of joy and pleasure born of composure (samādhijapītisukhasukhumasaccasaññā).
SN 48.40 states that any adventitious occurrence of unhappiness which may arise in the first jhāna due to the presence of directed thought and evaluation, ceases completely here in the second jhāna. What remains is the pleasure faculty (sukhindriya) and the happiness faculty (somanassindriya), which in light of SN 48.37, in the second jhāna refers to bodily pleasure (kāyika sukha) and mental happiness (cetasika sukha, i.e. somanassa).
This reading of the relevant sutta passages is also supported by the word-commentary for the second jhāna given in Peṭakopadesa 7.72:
With the constant cultivation of this same directed thought and evaluation his mind becomes inclined there. Then the directed thought and evaluation seem gross to him, as well as the joy and pleasure born of renunciation, and so joy and delight born of composure arise instead.
His mind, [which] had evaluation as an object-support, becomes internally serenely-clarified with the stilling of these [two factors of the first jhāna). The two phenomena, directed thought and evaluation, no longer need to be recollected, and what now can be served due to their stilling is the presently arisen unification which is singleness of mind. It is through unification that joy comes to fulfillment. The joy is the happiness faculty, while the pleasure is the pleasure faculty. The singleness of mind is meditative composure. So the second jhāna possesses four factors.
