To recap: Yoga is the state when the mind stuff stops whirling and because it is still our true nature is revealed. Our true nature is pure consciousness and whilst matter is essential it is also transitory, in contrast to the permanence of consciousness or energy. If everything is matter vibrating, the vibration is the constant, the matter the variables.
Patanjali builds from sutra to sutra so once a concept is expounded or presented subsequent sutras don’t reiterate it.
When we are not in a state of yoga, dwelling in union with Purusa (at other times, itaratra), we feel distinct, separate, our mind follows and takes the form (sarpuyam) of the whirls and fluctuations (vrtti).
If the mind is whirling we can not realise pure consciousness. For example when we become caught up in a web of emotions. the physical sensation of sadness or the sense of lightness which follows joy we are existing with an acute awareness of prakriti matter. We feel and we then identify with those feelings. We say “I am sad” or “I am happy” and whilst we are experiencing those emotions they fill our existence. It is difficult to recall the sensation of sadness when we are happy and vice versa.
Thus it takes practice to still the mind. In the meantime (spoiler alert) it takes faith that it can be stilled – More of this later……….