Alike in the Bhagavad-Gita and in the Yoga-sutras of Patanjali the terms are Samkhyan, and historically Yoga is based on the Samkhya, so far as its philosophy is concerned. Samkhya does not concern itself with, the existence of Deity, but only with the becoming of a universe, the order of evolution. Hence it is often called Nir-isvara Samkhya, the Samkhya without God. But so closely is it bound up with the Yoga system, that the latter is called Sesvara Samkhya, with God. For its understanding, therefore, I must outline part of the Samkhya philosophy, that part which deals with the relation of Spirit and matter; note the difference from this of the Vedantic conception of Self and Not-Self, and then find the reconciliation in the Theosophic statement of the facts in nature. The directions which fall from the lips of the Lord of Yoga in the Gita may sometimes seem to you opposed to each other and contradictory, because they sometimes are phrased in the Samkhyan and sometimes in the Vedantic terms, starting from different standpoints, one looking at the world from the standpoint of matter, the other from the standpoint of Spirit. If you are a student of Theosophy, then the knowledge of the facts will enable you to translate the different phrases. That reconciliation and understanding of these apparently contradictory phrases is the object to which I would ask your attention now.
The Samkhyan School starts with the statement that the universe consists of two factors, the first pair of opposites, Spirit and Matter, or more accurately Spirits and Matter. The Spirit is called Purusha—the Man; and each Spirit is an individual. Purusha is a unit, a unit of consciousness; they are all of the same nature, but distinct everlastingly the one from the other. Of these units there are many; countless Purushas are to be found in the world of men. But while they are countless in number they are identical in nature, they are homogeneous. Every Purusha has three characteristics, and these three are alike in all. One characteristic is awareness; it will become cognition. The second of the characteristics is life or prana; it will become activity. The third characteristic is immutability, the essence of eternity; it will become will. Eternity is not, as some mistakenly think, everlasting time. Everlasting time has nothing to do with eternity. Time and eternity are two altogether different things. Eternity is changeless, immutable, simultaneous. No succession in time, albeit everlasting—if such could be—could give eternity. The fact that Purusha has this attribute of immutability tells us that He is eternal; for changelessness is a mark of the eternal.
Such are the three attributes of Purusha, according to the Samkhya. Though these are not the same in nomenclature as the Vedantic Sat, Chit, Ananda, yet they are practically identical. Awareness or cognition is Chit; life or force is Sat; and immutability, the essence of eternity, is Ananda.