This question is the most puzzling in the Sāṃkhya doctrine. But careful penetration of the principles of Sāṃkhya-Yoga would make clear to us that this is a necessary and consistent outcome of the Sāṃkhya view of a dualistic universe.
For if it is said that purusha is one and we have the notion of different selves by his reflection into different minds, it follows that such notions as self, or personality, are false. For the only true being is the one, purusha. So the knower being false, the known also becomes false; the knower and the known having vanished, everything is reduced to that which we can in no way conceive. It may be argued that according to the Sāṃkhya philosophy also, the knower is false, for the pure purusha as such is not in any way connected with prakṛti. But even then it must be observed that the Sāṃkhya-Yoga view does not hold that the knower is false but analyses the nature of the ego and says that it is due to the seeming unity of the mind and purusha, both of which are reals in the strictest sense of the term. Purusha is there justly called the knower. He sees and simultaneously with this, there is a modification of buddhi (mind); this seeing becomes joined with this modification of buddhi and thus arises the ego, who perceives that particular form of the modification of buddhi. Purusha always remains the knower. Buddhi suffers modifications and at the same time catches a glimpse of the light of purusha, so that contact (saṃyoga) of purusha and prakṛti occurs at one and the same point of time, in which there is unity of the reflection of purusha and the particular transformation of buddhi.
The knower, the ego and the knowable, are none of them false in the Sāṃkhya-Yoga system at the stage preceding kaivalya, when buddhi becomes as pure as purusha; its modification resembles the exact form of purusha and then purusha knows himself in his true nature in buddhi; after which buddhi vanishes. The Vedānta has to admit the modifications of māyā, but must at the same time hold it to be unreal. The Vedānta says that māyā is as beginningless as prakṛti yet has an ending with reference to the released person as the buddhi of the Sāṃkhyists.
But according to the Vedānta philosophy, knowledge of ego is only false knowledge—an illusion as many imposed upon the formless Brahman. Māyā, according to the Vedāntist, can neither be said to exist nor to non-exist. It is anirvācyā, i.e. can never be described or defined. Such an unknown and unknowable māyā causes the Many of the world by reflection upon the Brahman. But according to the Sāṃkhya doctrine, prakṛti is as real as purusha himself. Prakṛti and purusha are two irreducible metaphysical remainders whose connection is beginningless (anādisaṃyoga). But this connection is not unreal in the Vedānta sense of the term. We see that according to the Vedānta system, all notions of ego or personality are false and are originated by the illusive action of the māyā, so that when they ultimately vanish there are no other remainders. But this is not the case with Sāṃkhya, for as purusha is the real seer, his cognitions cannot be dismissed as unreal, and so purushas or knowers as they appear to us to be, must be held real. As prakṛti is not the māyā of the Vedāntist (the nature of whose influence over the spiritual principle cannot be determined) we cannot account for the plurality of purushas by supposing that one purusha is being reflected into many minds and generating the many egos. For in that case it will be difficult to explain the plurality of their appearances in the minds (buddhis). For if there be one spiritual principle, how should we account for the supposed plurality of the buddhis? For we should rather expect to find one buddhi and not many to serve the supposed one purusha, and this will only mean that there can be only one ego, his enjoyment and release. Supposing for argument’s sake that there are many buddhis and one purusha, which reflected in them, is the cause of the plurality of selves, then we cannot see how prakṛti is moving for the enjoyment and release of one purusha; it would rather appear to be moved for the sake of the enjoyment and release of the reflected or unreal self. For purusha is not finally released with the release of any number of particular individual selves. For it may be released with reference to one individual but remain bound to others. So prakṛti would not really be moved in this hypothetical case for the sake of purusha, but for the sake of the reflected selves only. If we wish to avoid the said difficulties, then with the release of one purusha, all purushas will have to be released. For in the supposed theory there would not really be many different purushas, but the one purusha appearing as many, so that with his release all the other so-called purushas must be released. We see that if it is the enjoyment (bhoga) and salvation (apavarga) of one purusha which appear as so many different series of enjoyments and emancipations, then with his experiences all should have the same experiences. With his birth and death, all should be born or all should die at once. For, indeed, it is the experiences of one purusha which appear in all the seeming different purushas. And in the other suppositions there is neither emancipation nor enjoyment by purusha at all. For there, it is only the illusory self that enjoys or releases himself. By his release no purusha is really released at all. So the fundamental conception of prakṛti as moving for the sake of the enjoyment and release of purusha has to be abandoned.
So we see that from the position in which Sāṃkhya and Yoga stood, this plurality of the purushas was the most consistent thing that they could think of. Any compromise with the Vedānta doctrine here would have greatly changed the philosophical aspect and value of the Sāṃkhya philosophy. As the purushas are nothing but pure intelligences they can as well be all-pervading though many. But there is another objection that, since number is a conception of the phenomenal mind, how then can it be applied to the purushas which are said to be many?[[18]] But that difficulty remains unaltered even if we regard the purusha as one. When we go into the domain of metaphysics and try to represent Reality with the symbols of our phenomenal conceptions we have really to commit almost a violence towards it. But we must perforce do this in all our attempts to express in our own terms that pure, inexpressible, free illumination which exists in and for itself beyond the range of any mediation by the concepts or images of our mind. So we see that Sāṃkhya was not inconsistent in holding the doctrine of the plurality of the purushas. Patañjali does not say anything about it, since he is more anxious to discuss other things connected with the presupposition of the plurality of purusha. Thus he speaks of it only in one place as quoted above and says that though for a released person this world disappears altogether, still it remains unchanged in respect to all the other purushas.
CHAPTER III
THE REALITY OF THE EXTERNAL WORLD
We may now come to the attempt of Yoga to prove the reality of an external world as against the idealistic Buddhists. In sūtra 12 of the chapter on kaivalya we find: “The past and the future exist in reality, since all qualities of things manifest themselves in these three different ways. The future is the manifestation which is to be. The past is the appearance which has been experienced. The present is that which is in active operation. It is this threefold substance which is the object of knowledge. If it did not exist in reality, there would not exist a knowledge thereof. How could there be knowledge in the absence of anything knowable? For this reason the past and present in reality exist.”[[19]]
So we see that the present holding within itself the past and the future exists in reality. For the past though it has been negated has really been preserved and kept in the present, and the future also though it has not made its appearance yet exists potentially in the present. So, as we know the past and the future worlds in the present, they both exist and subsist in the present. That which once existed cannot die, and that which never existed cannot come to be (nāstyasataḥ saṃbhavaḥ na cāsti sato vināsāḥ, Vyāsa-bhāshya, V. 12). So the past has not been destroyed but has rather shifted its position and hidden itself in the body of the present, and the future that has not made its appearance exists in the present only in a potential form. It cannot be argued, as Vācaspati says, that because the past and the future are not present therefore they do not exist, for if the past and future do not exist how can there be a present also, since its existence also is only relative? So all the three exist as truly as any one of them, and the only difference among them is the different way or mode of their existence.
He next proceeds to refute the arguments of those idealists who hold that since the external knowables never exist independently of our knowledge of them, their separate external existence as such may be denied. Since it is by knowledge alone that the external knowables can present themselves to us we may infer that there is really no knowable external reality apart from knowledge of it, just as we see that in dream-states knowledge can exist apart from the reality of any external world.
So it may be argued that there is, indeed, no external reality as it appears to us. The Buddhists, for example, hold that a blue thing and knowledge of it as blue are identical owing to the maxim that things which are invariably perceived together are one (sahopalambhaniyamādabhedo nīlataddhiyoḥ). So they say that external reality is not different from our idea of it. To this it may be replied that if, as you say, external reality is identical with my ideas and there is no other external reality existing as such outside my ideas, why then does it appear as existing apart, outside and independent of my ideas? The idealists have no basis for the denial of external reality, and for their assertion that it is only the creation of our imagination like experiences in dreams. Even our ideas carry with them the notion that reality exists outside our mental experiences. If all our percepts and notions as this and that arise only by virtue of the influence of the external world, how can they deny the existence of the external world as such? The objective world is present by its own power. How then can this objective world be given up on the strength of mere logical or speculative abstraction?