Man gains his knowledge of the outside world through his senses. And, consequently, many of us are in the habit of thinking of these senses as if _they_ did the sensing, instead of being merely carriers of the vibrations coming from the outside world, which are then presented to the Mind for examination. We shall speak of this at greater length a little later on in this lesson. Just now we wish to impress upon you the fact that it is the Mind that perceives, not the senses. And, consequently, a development of Perception is really a development of the Mind. The Yogis put their students through a very arduous course of practice and exercises designed to develop their powers of perception. To many this would appear to be merely a development of the Senses, which might appear odd in view of the fact that the Yogis are constantly preaching the folly of being governed and ruled by the senses. But there is nothing paradoxical about all this, for the Yogis, while preaching the folly of sense life, and manifesting the teaching in their lives, nevertheless believe in any and all exercises calculated to "sharpen" the Mind, and develop it to a keen state and condition. They see a great difference between having a sharpened perception, on the one hand, and being a slave to the senses on the other. For instance, what would be thought of a man who objected to acquiring a keen eyesight, for fear it would lead him away from higher things, by reason of his becoming attached to the beautiful things he might see. To realize the folly of this idea, one may look at its logical conclusion, which would be that one would then be much better off if all their senses were destroyed. The absurdity, not to say wickedness, of such an idea will be apparent to everyone, after a minute's consideration. The secret of the Yogi theory and teachings regarding the development of the Mental powers, lies in the word "_Mastery_." The Yoga student accomplishes and attains this mastery in two ways. The first way is by subordinating all the feelings, sense-impressions, etc., to the Mastery of the "I," or Will, the Mastery being obtained in this way by the assertion of the dominancy of the "I" over the faculties and emotions, etc. The second step, or way, lies in the Yogi, once having asserted the mastery, beginning to develop and perfect the Mental instrument, so as to get better work and returns from it. In this way he increases his kingdom and is Master over a much larger territory.