If you want to understand Buddhism it is necessary for you to forget all about your preconceived ideas. To begin with, you must give up the idea of substantiality or existence. The usual view of life is firmly rooted in the idea of existence. For most people everything exists; they think whatever they see and whatever they hear exists. Of course the bird we see and hear exists. It exists, but what I mean by that may not be exactly what you mean. The Buddhist understanding of life includes both existence and nonexistence. The bird both exists and does not exist at the same time. We say that a view of life based on existence alone is heretical. If you take things too seriously, as if they existed substantially or permanently, you are called a heretic. Most people may be heretics.
We say true existence comes from emptiness and goes back again into emptiness. What appears from emptiness is true existence. We have to go through the gate of emptiness. This idea of existence is very difficult to explain. Many people these days have begun to feel, at least intellectually, the emptiness of the modern world, or the self-contradiction of their culture. In the past, for instance, the Japanese people had a firm confidence in the permanent existence of their culture and their traditional way of life, but since they lost the war, they have become very skeptical. Some people think this skeptical attitude is awful, but actually it is better than the old attitude.
As long as we have some definite idea about or some hope in the future, we cannot really be serious with the moment that exists right now. You may say, “I can do it tomorrow, or next year,” believing that something that exists today will exist tomorrow. Even though you are not trying so hard, you expect that some promising thing will come, as long as you follow a certain way. But there is no certain way that exists permanently. There is no way set up for us. Moment after moment we have to find our own way. Some idea of perfection, or some perfect way which is set up by someone else, is not the true way for us.

Each one of us must make his own true way, and when we do, that way will express the universal way. This is the mystery. When you understand one thing through and through, you understand everything. When you try to understand everything, you will not understand anything. The best way is to understand yourself, and then you will understand everything. So when you try hard to make your own way, you will help others, and you will be helped by others. Before you make your own way you cannot help anyone, and no one can help you. To be independent in this true sense, we have to forget everything which we have in our mind and discover something quite new and different moment after moment. This is how we live in this world.

So we say true understanding will come out of emptiness. When you study Buddhism, you should have a general house cleaning of your mind. You must take everything out of your room and clean it thoroughly. If it is necessary, you may bring everything back in again. You may want many things, so one by one you can bring them back. But if they are not necessary, there is no need to keep them.

We see the flying bird. Sometimes we see the trace of it. Actually we cannot see the trace of a flying bird, but sometimes we feel as if we could. This is also good. If it is necessary, you should bring back in the things you took from your room. But before you put something in your room, it is necessary for you to take out something. If you do not, your room will become crowded with old, useless junk.

We say, “Step by step I stop the sound of the murmuring brook.” When you walk along the brook you will hear the water running. The sound is continuous, but you must be able to stop it if you want to stop it. This is freedom; this is renunciation. One after another you will have various thoughts in your mind, but if you want to stop your thinking you can. So when you are able to stop the sound of the murmuring brook, you will appreciate the feeling of your work. But as long as you have some fixed idea or are caught by some habitual way of doing things, you cannot appreciate things in their true sense.

If you seek for freedom, you cannot find it. Absolute freedom itself is necessary before you can acquire absolute freedom. That is our practice. Our way is not always to go in one direction. Sometimes we go east; sometimes we go west. To go one mile to the west means to go back one mile to the east. Usually if you go one mile to the east it is the opposite of going one mile to the west. But if it is possible to go one mile to the east, that means it is possible to go one mile to the west. This is freedom. Without this freedom you cannot be concentrated on what you do. You may think you are concentrated on something, but before you obtain this freedom, you will have some uneasiness in what you are doing. Because you are bound by some idea of going east or west, your activity is in dichotomy or duality. As long as you are caught by duality you cannot attain absolute freedom, and you cannot concentrate.

Concentration is not to try hard to watch something. In zazen if you try to look at one spot you will be tired in about five minutes. This is not concentration. Concentration means freedom. So your effort should be directed at nothing. You should be concentrated on nothing. In zazen practice we say your mind should be concentrated on your breathing, but the way to keep your mind on your breathing is to forget all about yourself and just to sit and feel your breathing. If you are concentrated on your breathing you will forget yourself, and if you forget yourself you will be concentrated on your breathing. I do not know which is first. So actually there is no need to try too hard to be concentrated on your breathing. Just do as much as you can. If you continue this practice, eventually you will experience the true existence which comes from emptiness.