Concentration means intensifying the power of assimilation. (I.157)

Concentration is the essence of all Knowledge; nothing can be done without it. Ninety percent of thought force is wasted by the ordinary human being, and therefore he is constantly committing blunders; the trained man or mind never makes a mistake. (VI.123-124)

To me the very essence of education is concentration of mind, not the collecting of facts. If I had to do my education over again, and had any voice in the matter, I would not study facts at all. I would develop the power of concentration and detachment, and then with a perfect instrument I could collect facts at will. (VI.38-39)

Take up one idea. Make that one idea your life – think of it, dream of it, live on that idea. Let the brain, muscles, nerves, every part of your body, be full of that idea, and just leave every other idea alone. This is the way to success. If we really want to be blessed, and make others blessed, we must go deeper. (I.177)

There is only one method by which to attain knowledge, that which is called concentration. (I.130)

All success in any line of work is the result of this. High achievements in art, music, etc., are the results of concentration. (VI.37)

The power of concentration is the only key to the treasure house of knowledge. In the present state of our body we are so much distracted, and the mind is frittering away its energies upon a hundred sorts of things. As soon as I try to calm my thoughts and concentrate my mind upon one object of knowledge, thousands of undesired impulses rush into the brain, thousands of thoughts rush into the mind and disturb it. How to check it and bring the mind under control is the whole subject of study in Raja-Yoga. (II.391)

The main difference between men and the animals is the difference in their power of concentration. An animal has very little power of concentration. Those who have trained animals find much difficulty in the fact that the animal is constantly forgetting what is told him. He cannot concentrate his mind long upon anything at a time. The difference in their power of concentration also constitutes the difference between man and man. Compare the lowest with the highest man. The difference is in the degree of concentration. (VI.37)

We have but one method of acquiring knowledge. From the lowest man to the highest yogi, all have to use the same method; and that method is what is called concentration. The chemist who works in his laboratory concentrates all the powers of his mind, brings them into one focus, and throws them on the elements; and the elements stand analyzed, and thus his knowledge comes. The astronomer has also concentrated the powers of his mind and brought them into one focus; and he throws them on to objects through his telescope; and stars and systems role forward and give up their secrets to him. So it is in every case with the professor in his chair, the student with his book – with every man who is working to know. The more this power of concentration, the more knowledge is acquired. (II.390-391)

How has all the knowledge in the world been gained but by the concentration of the powers of the mind? The world is ready to give up its secrets if we know how to knock, how to give it the necessary blow. The strength and force of the blow come through concentration. There is no limit to the power of human mind. The more concentrated it is, the more power is brought to bear on one point; that is the secret. (I 131-132)