The science of Raja-Yoga, in the first place, proposes to give us such a means of observing the internal states. The instrument is the mind itself. The power of attention, when properly guided, and directed towards the internal world, will analyse the mind, and illumine facts for us. The powers of the mind are like rays of light dissipated; when they are concentrated, they illumine. This is our only means of knowledge. Everyone is using it, both in the external and the internal world; but, for the psychologist, the same minute observation has to be directed to the internal world, which the scientific man directs to the external; and this requires a great deal of practice. From our childhood upwards we have been taught only to pay attention to things external, but never to things internal; hence most of us have nearly lost the faculty of observing the internal mechanism. To turn the mind as it were, inside, stop it from going outside, and then to concentrate all its powers, and throw them upon the mind itself, in order that it may know its own nature, analyse itself, is very hard work. Yet that is the only way to anything which will be a scientific approach to the subject.