Unfortunately, the confusion about Patañjali's life permeates the very thing for which he is the most famous: the Yoga Sutras. There is uncertainty about (at least) three important things. Did Patañjali actually write the Yoga Sutras? If he did, did he make an original contribution or was he 'merely' a collator and systematizer? And assuming that the answer to the first question is affirmative, is the text we have today what Patañjali actually wrote?
Probably the greatest controversy concerns the fourth pada or chapter of the Yoga Sutras. Some commentators argue that its style and content are very different from the first three. For one thing, it is exceptionally short. This brevity would not amount to much if it were not for the structure of its argument. The first three chapters seem to develop their themes in a leisurely and non-dogmatic manner. The fourth, by contrast, seems much more rushed. It has the air of striving earnestly to make a point. Sutra 16 is probably the most controversial of all in that it seems to have been lifted from Vyasa's seventh commentary. At one point Vyasa seems to be expounding on Patañjali and countering arguments raised by Buddhism. At another moment he seems to be saying that a particular sentence he is elucidating is in any case something Patañjali said. But—it is unclear if Patañjali actually said it, or if Vyasa merely says he did.
Another bone of contention is that, unlike the first two chapters, the third ends with 'iti'. 'Iti' has the rough meaning of 'thus as it was intended' (somewhat like the QED or quod erat demonstrandum of mediaeval and Renaissance geometric texts). It is the traditional way of ending a Sanskrit text—meaning that there seem to be two 'The End's in one book. The critics declare that it is most curious that one book should contain two 'iti's or 'The End's.
Those who prefer to affirm the unity of the Yoga Sutras are unconvinced by the above arguments. They point out that the fourth chapter is physically and metaphysically coherent with the previous three and that the four, taken together, achieve a remarkable degree of homogeneity and thematic consistency. All the fourth chapter does is describe the same topic—but from the standpoint of one who has succeeded rather than one who is still seeking. The sceptics promptly counter by saying that anyone wanting to pass off an obviously later interpolation as a part of the original would have gone to exactly this kind of trouble. Clearly, it is important to settle whether the first three chapters, which both sides use as their measuring stick, are indisputable as Patañjali originals. Settling even this becomes difficult because the status of some sutras (with sutra 22 in Chapter III being probably the most famous example) has also been questioned. It, also, say the critics, seems to be a later interpolation in that it disturbs an otherwise smooth flow. The obvious response is then made. This authenticity debate is not one that can really be resolved.
As for what precise contribution Patañjali made, this is also hard to settle. Yoga, or some yoga-like subject, definitely existed before him. The oldest of the Upanishads make unequivocal references to, for example, pranayama, the science of the breath. The later Katha Upanishad, amongst half a dozen others of the same vintage, indicates that that era already enjoyed several different systems of yoga. This differentiation bespeaks a long ancestry. The more specifically yogic Upanishads, such as the Hamsa, the Yogatattva, the Yogakundali and some half a dozen others, are later still and give instructions—admittedly obscure—for asanas and other yogic disciplines. Although yoga is ultimately about practice, it is also a philosophy and a metaphysic. Of the Upanishads, probably only the Maitrayana has a distinct leaning towards the Sankhya philosophy—something that is essential for the full emergence of yoga as a system of thought. Yoga is complementary to Sankhya. It has the goal of realizing the Spirit from within the world of nature as discussed in Sankhya. By the time of the Mahabharata—the great epic that is effectively the early history of India—both Sankhya and Yoga are being taken for granted as pre-existing and already ancient systems of thought. It is therefore appropriate that they have founders. Kapila has become the fountainhead for Sankhya while Hiranyagarbha fulfills a similar role for yoga. According to the Ahirbudhnya, Hiranyagarbha revealed the whole of yoga in the Nirodha Samhita and Karma Samhita. And ... it is surely beyond coincidence that the second sutra of the Yoga Sutras defines yoga in terms of nirodha. Not only that, but the Nirodha Samhita is often called the Yoganushasanam ... the very words with which Patañjali begins the Yoga Sutras. If Patañjali did make original contributions then he borrowed heavily from pre-existing trends in Sankhya and Yoga.
As to the question of originality, although Patañjali (at least, as evidenced in his Yoga Sutras) is clearly of the lineage of Hiranyagarbha and Kapila, he does differ from them in important respects. This could have been because he had genuinely had ideas of his own. But yoga was strongly associated with the shramana tradition, these being wandering forest mendicants and seekers. It therefore encouraged independence of thought. So Patañjali could just as well have been trying to bring order to a system with widely divergent methods. Some insist that 'all' he did was bring together and summarize a varied body of texts most of which have now been lost. Whatever was his inspiration, Patañjali does seem to have propounded many ideas that were not of the mainstream in either Sankhya or Yoga. He recognizes ego, for example, but does not accept it is a separate principle. He recognizes the subtle body but does not regard it as permanent. He also denies that it can operate directly on external things. These ideas differ from the mainstream, at that time, in both Sankhya and Yoga. Like all others concerning Patañjali the question of what is original with him is well nigh impossible to settle. The Yoga Sutras could easily have been his original thoughts on both Sankhya and Yoga. On the other hand, he could have been reinterpreting and clarifying what others had said, freeing them at the same time from contradictions. The very least that can be said is that he brought many threads, some dating back to the Vedas and Upanishads, together; and that he did so with what modern psychology would call genius. What had previously been long-winded and obscure he encapsulated in the nuggets of his sutras; and what had previously been abstract he made practical and easy to validate through the lives and experiences of a long line of teachers and practitioners. While the Yoga Sutras initially appears to be a dry and theoretical text, it explains human nature and psychology while also being an intensely practical manual for spiritual advancement.
Ultimately, the historical uncertainties concerning Patañjali are of little concern to those who wish to achieve some measure of success in the things of which he wrote: gaining inner tranquillity and attaining spiritual realization. Its authorship and genesis may be contested but the Yoga Sutras is a coherent and self-sustaining whole that supports the seeking aspirant on theoretical and practical levels. A part of the reason for its longevity and the high regard in which it is held is that Patañjali provided a framework capable of supporting the vastly different modes of comprehension and understanding that one person goes through over a lifetime; that many make over cultures; and that the human consciousness to which Patañjali spoke so eloquently makes over epochs.