Yoga is controlling of thoughts arising in the mind. When thoughts are controlled or prevented through practice, the seer or practitioner(yogi) rests in his true self or soul(atman). Either you remain in true self or control thoughts, the other will result automatically. In true self one shall not see or hear anything. Because there is none other than the self. When there is anything other than the self, one shall see or hear something. When everything has merged in the pure consciousness of the true self, when there is none other than the self, what is to see or hear?
Everybody has this experience in deep sleep. In the waking and dreaming states everybody sees or hear something. But when one enters into deep sleep nothing is seen or heard of. This is because the mind and senses are immersed in the pure consciousness of an individual. With the mind and senses all objects, all worlds, all desires are immersed in pure consciousness. For this one feels the bliss after a sound sleep. This bliss is very less in comparison to the bliss one may feel by resting in true self consciously or knowingly.
A practitioner(yogi) does not always remain in true self. In the other state or when he is not in a yogic state, he remains in his thoughts(I.4). As a being navigates between waking, dreaming and deep sleep states, so a Yogi either remains in true self or remains in thoughts and actions. In that state self, mind and thought become one. For this a yogi achieves whatever he desires, because soul is all powerful. He knows how to put his self in his thought or action.
Patanjali describes that there are five types of thoughts and each thought may either be of pleasure or of pain(I.5). Thoughts are of five types because we have five sense organs. The thought related to each sense organ may either be of pleasure or of pain. The sight of children playing is of pleasure whereas the sight of a dead body is of pain. This way there are ten types of thoughts.
Patanjali in his Yogasutra further describes – each of these ten types of thoughts may further be divided into five types based on proof(pramana), opposite(viparyay), alternative(vikalpa), sleep(nidra) or memory(smriti)(I.6). So in all there are fifty types of thoughts.
Thoughts based on proof are perceived directly through senses or through mind. Senses perceive the outside worldly objects and mind realises the true self. So there should not be doubt regarding there presence. Existence of sun or moon is a proven thought. If a blind believes that sun or moon does not exist, he is in opposite thought or opinion. If a man believes that he has no self or soul or soul is inferior to someone called God, he is in opposite thought or dualism. The Upanishads declare that soul is Brahman, the ultimate Reality. When people cannot perceive a thing directly and remain in opposite thoughts, they depend upon alternative or imaginary thoughts.
People cannot perceive God directly and for that they make statues of Gods and Goddesses and compose mythology and believe in them. Thoughts categorised as sleep lack all kinds of sound knowledge or consciousness. People remain in perpetual darkness of ignorance. Mindless and irrational social and religious practices are nothing but ignorance. Such ignorance is stored up in the mind as memory. It hides the truth and one fails to understand the importance of proven thoughts. Spiritual and yogic upliftment is possible only when one accepts the proven thoughts.