The fourth thought is to realize the brevity of life. I don't know when I'm going to die. Were I to die now, without accomplishing my practice, it would be very unfortunate. If I have only one spurt of energy left, I should put that energy into practice. Whether I can get enlightened or not is another question. At least I haven't failed myself; I've done justice to myself. And in the next life, probably I can continue practicing. If I were to die in idleness, in my next birth my karma may not be so good as to allow me to continue practicing. So to do justice to myself, and recognizing the brevity of life I should put my whole being into practice. Great Angry Determination is actually this attitude of great earnestness and great diligence.
Most people cannot generate this Angry Determination, nor can they pretend to have it. If they try to generate it, their minds will be very confused and scattered, and they will have a lot of vexations. Only after practicing for some time, when one has Great Faith and Great Vow, when one's mind is settled, when one's health is good, it is possible in that state to slip into idleness and looseness. In such a situation, one should still try to generate Angry Determination. Just thinking will not make it happen, but you will at least be alert to your condition, and that can help you move forward again. But unless the two previous conditions are already fulfilled, trying to arouse Angry Determination can only produce scatteredness, vexation, and anger. This may result in disappointment and disillusion, but not Angry Determination.
We come now to Great Doubt. Great Doubt is possible, or is forceful, only when the mind is very much stable and unified. At this point, you will probably be using a hua-t'ou or kung-an. In most cases these practices come from the tradition, recorded and handed down by patriarchs and masters, but not always. It is possible for the practitioner to spontaneously generate a question, a great doubt, in his mind. And in such a situation he can simply pursue the hua-t'ou which arises spontaneously. So what is Great Doubt? It is a question, the answer to which is of the utmost importance to the practitioner. His attitude is one of great anxiousness to find the answer. And yet he cannot use any reasoning or logic, or rely on his knowledge or experience. He can only pursue the question, continue questioning without interruption.