The koan, then, is the final step in the "auxiliary means." A succinct analysis of the koan technique is provided by Ruth F. Sasaki in _Zen Dust_: "Briefly, [koans] consisted of questions the early masters had asked individual students, together with the answers given by the students; questions put to the masters by students in personal talks or in the course of the masters' lectures, together with the masters' answers; statements of formulas in which the masters had pointed to the profound Principle; anecdotes from the daily life of the masters in which their attitudes or actions illustrated the functioning of the Principle; and occasionally a phrase from a sutra in which the Principle or some aspect of it was crystallized in words. By presenting a student with one or another of these koans and observing his reaction to it, the degree or depth of his realization could be judged. The koans were the criteria of attainment."2
Called _kung-an _in Chinese (meaning a "case" or a problem), the koan was a response to two major challenges that beset Ch'an in the Sung era: First, the large number of students that appeared at Ch'an monasteries as a result of the demise of other sects meant that some new means was needed to preserve personalized attention (some masters reportedly had one thousand or even two thousand followers at a monastery); and second, there was a noticeable decline in the spontaneity of both novices and masters. The masters had lost much of the creative fire of Ch'an's Golden Age, and the novices were caught up in the intellectual, literary world of the Sung, to the point that intellectualism actually threatened the vitality of the sect.
The koan, then, was the answer to this dilemma. It systematized instruction such that large numbers of students could be treated to the finest antirational tradition of the Ch'an sect, and it rescued the dynamism of the earlier centuries. Although mention of kung-an occurs in the Ch'an literature before the end of the T'ang era (618-907), the reference was to a master's use of a particularly effectual question on more than one student. This was still an instance of a master using his own questions or paradoxes. The koan in its true form--that is, the use of a classic incident from the literature, posed as a conundrum--is said to have been created when a descendant of Lin-chi, in the third generation, interviewed a novice about some of Lin-chi's sayings.3 This systematic use of the existing literature was found effective, and soon a new teaching technique was in the making.