This is not an achievement. But, if by science is meant technological inventions, setting up of factories and industrial organisation, science is a bane on human life. It will not help us, because it carries us further away from the centre of reality, and compels us to affirm more and more that the world is outside us, rather than the fact that we are inseparable from the world. The science of Yoga, therefore, is a psychology of a philosophical nature. Patanjali does not go into the details of the philosophical background of the necessity to control the mind, the background that comes in Samkhya and Vedanta.
Yoga is control of the mind, restraint of the mind-stuff.
The moment we hear this, we begin to get excited. Yoga is control of the mind. Therefore, we have to control ourselves. That is an unfortunate result that often follows from an over-enthusiasm, emotionally aroused in ourselves by hearing the very word Yoga. We should not be stirred up into an emotion, just because we listen to the word Yoga mentioned by somebody.