The Buddhist Philosophy is in many respects in similar to the Samkhya Philosophy. Consider the following observations with this respect:
1. Both reject sacrificial ritualism
2. Both are humanistic
3. Both reject any divine grace for attaining moksa or enlightment
4. Both reject the idea of spirit / soul
Which among the above observations is / are correct?

Answer: [A] Only 1, 2 & 3

Both reject sacrificial ritualism

There are some basic points of agreement towards which both Samkhya-Yoga and Buddhism were drawn. Their approach is positive and pragmatic.  This positivistic attitude is reflected in their rejection of sacrificial ritualism, priests, God, etc. Buddha’s antipathy towards sacrifice and violence is well known. But Samkhya being in the fold of orthodox systems also renounces the ritualistic way unable to solve the problem of suffering. Samkhya Philosophy says that sacrificial rituals are like the ordinary perceptible means; hence ultimately ineffective in bringing that abiding and final release from suffering. Samkhya goes to the extent describing one form of bondage, “Bondage by sacrificial gifts.”

Both are Humanistic

Both reject any divine grace for attaining moksa or enlightment

Both Samkhya and Buddhism are humanistic. The goal is achievable by everyone by his own effort; one need not look for any divine grace for attaining moksa. Every liberated man attains to the self-effulgent nature of the isolated Purusa (Kevalin) or Buddhahood by following the prescribed method. A man must depend entirely on himself, as the canonical text says: ‘you yourselves must make the effort; the Buddhas do but point the way’.

Both reject the idea of spirit / soul

Both Samkhya and the early Buddhism rejected the concept of soul. They emphasis on individual rather on cosmic; similarity in the theories of evolution; similarity in the view of the world as a constantly becoming and changing phenomena; acceptance of the concept of Gunas; acceptance of the Satkarya vada that the effect resides in its cause;   similarity in enumeration of the basic elements or components of nature; similarity in the notions of liberation kaivalya or nirvana;   rejection of both the Vedic authority and the validity of rituals; rejection of extreme practices and self torture etc.

The Samkhya abandons the idea of the existence of the absolute, but it retains the idea of spirit (Purusha) and of material world (Prakrti); the Buddhism, on the other hand abandoned both these two conceptions, and retained only the fleeting series of mental states (stream of consciousness) as a quasi reality, In either case there is effort to disown the human psycho-physical apparatus and its functioning.

This question is a part of GKToday's Integrated IAS General Studies Module