The investigation of hwadu is that one must take up only one hwadu and continually study it. One must not change hwadu indiscriminately. The change of hwadu derives from an insufficient faith in the teacher. If one has complete faith in the teacher who gave one the hwadu, one will not even entertain the slightest thought of investigating another hwadu.
A practitioner should only immerse himself in the one hwadu presented by the teacher, no matter what hwadu it is. This is because if one conquers one hwadu one will be naturally enlightened by other hwadu. Seon Master Dahui said, “Since a thousand or ten thousand doubts are only one doubt, if one conquers doubt in only one hwadu, one simultaneously conquers a thousand or ten thousand doubts.” And he said, “If one clearly discerns one, one discerns all, just as if one cuts a skein of thread. If one cuts it once, one simultaneously cuts all (the threads).”
No matter what hwadu it is, if one conquers only that hwadu one will conquer all 1,700 hwadu. Therefore it is not necessary to change various hwadu and investigate them. If one looks at the realities of taking up hwadu of recent times, there are some people who receive one hwadu, but when it does not work out even a bit, if they wish they try to take up another hwadu. But one should not constantly change hwadu in this way. In fact, in conditions where the mental resolution does not work, it is not easy to take up a hwadu. And so, if one takes up this hwadu and one is not obsessed by it, taking up another hwadu in the end likewise means one will not be obsessed by it. While one goes on changing hwadu a number of times and one takes them up, neither gruel nor rice will do, and one will only waste one’s valuable time. Just as a well-digger who digs a little here and a little there in the end will not get any water, one cannot promise a good result by changing hwadu as one wishes.
To emphasize it, one must enter into, earnestly doubt, and have the sole hwadu presented by the teacher. Therefore Seon Master Naong said, “At all costs do not investigate one and then change it for another hwadu. All day long, whatever you do, you must just take up only one hwadu.”
Even if one is not well obsessed with a hwadu, if one tries to take it up untiringly and without ease, one day the time will come when one will naturally be obsessed by it. When we do archery, at first the arrow frequently misses the target, but if one tries to continue it a number of times, in the end one hits the target exactly. Taking up hwadu is the same. If one tries to tirelessly and closely investigate the hwadu, the time when one is obsessed with hwadu will come naturally. The mental attitude that pushes on consistently not putting aside the hwadu, with the serious mind that “if I am not awakened in this life, when in this body will I be saved and in which life” is important. One has to take up the hwadu maintaining a fierce spirit endlessly thought by thought, when one goes to the toilet or when eating, or sitting and lying down, coming and going, day and night.
In this way it is important that one has one hwadu and scrupulously acts on it, and one must not practice by changing the hwadu frequently. If one looks at the recorded sayings of various Seon masters, one can know that nearly all of them investigated only one hwadu during their entire life. In cases when one truly cannot do anything one can practice by changing the hwadu at the direction of one’s master.