Its application is by stages
Its application is by stages. Its application the practice of that samādhi as it has to be done is by stages: external things are taken as objects of the meditation (dhyāna), and then internal things, and then such things as the three-fold changes of which he is going to speak (III. 16).
That saṃyama is to be practised by moving on to the next stage only when the first stage has been mastered. For if an early stage is not mastered, but missed out in favour of jumping on to the next stage, he will not attain saṃyama on the later stages at all. And without that, how will the knowledge-light ever arise?
(But) for one who has mastered later stages, saṃyama practice on earlier stages such as telepathy would not be right. Why not? Because the purpose will have been attained already in another way.
That saṃyama is to be practised, to be done by the one rightly determined to master the stages by moving on to the next stage only when the first stage has been mastered: the yogin having fixed his meditation on some stage till he has attained saṃyama on it, goes on to the stage next after the saṃyama which he has mastered.
So when it is said (in III.44) that in saṃyama on elements like earth, the physical aspect, the essential nature, the subtle aspect, the inherent aspect, and the aspect of purposefulness are to be mastered in turn, it means that having performed saṃyama on the physical, the next saṃyama has to be on the essential only, which follows on the one that has been mastered. He should not pass over the essential nature and go on to the later aspects such as the subtle nature.
Why not? Because if an earlier stage is not mastered, but missed out in favour of jumping to the next stage, he will not attain saṃyama on later stages on subsequent stages at all. If, without having mastered the next in order, he tries to practise saṃyama on those that come later, he will not attain saṃyama on them, and that non-attainment will mean failure for him. And without that if he does not attain saṃyama on the later stages how will knowledge-light ever arise? For there would be nothing to bring it about: there can be no lamplight unless the oil, wick, and a flame are brought together.
For one who has mastered later stages a yogin who has mastered later stages such as (realization of) ātman, saṃyama practice on earlier stages such as telepathy would not be right. Why not? Because the purpose the later stages such as ātman-realization will have been attained in another way, quite different from such petty stages as telepathy. From things like telepathy there arises confusion, because their nature is absence of discriminative knowledge (viveka). For one whose saṃyama is on the later stages, to take the thoughts of others as object would mean to make a confusion in his own mind, though trained in yoga, and so it would not be right. For he will have already attained his purpose, ātman-realization, in a different way, by discrimination.
But others understand it as meaning that his purpose is telepathy, and that it is this which has been attained in another way. They say it is just by the higher stages such as ātman-realization that the aim, telepathy, is accomplished. But if this had been the meaning, it would have been said that saṃyama practice on earlier stages would not be needed, but not that it would not be right. The fact that the words not right are used implies that it is wrong.
As to the question: What stage is to come next after this one? On this, it is yoga alone that is the teacher. How so? It has been said
Yoga is to be known by yoga;
Yoga goes forward from yoga alone.
He who is not careless in his yoga,
For a long time sports in the yoga-s.
As to the question: What stage is to come next after this one? – when one stage has been mastered, how is it to be decided what should come next? On this, it is yoga alone that is the teacher. ‘Yoga’ here means the attainment of saṃyama on the previous stage, and it is by that alone that one understands which is to be the next one.
How so? It has been said: Yoga is to be known by yoga. By the yoga which consists of the attainment of the previous saṃyama, the object of yoga which is to come next will be known. And this Yoga, saṃyama, goes forward becomes clear from yoga alone, from attainment of saṃyama on the previous stages alone.
Just as one blind from birth, ascending a flight of steps, from the feel of his foot on the first step knows confidently where the next one is, so Yoga goes forward from yoga.
Therefore he who knows this, who is not careless in his yoga who is restrained in yoga., for a long time sports in the yogas, in the fruits of yogic powers.