It is said that a hunter named Jara accidentally killed Krishna while Krishna was deep in meditation in the forests. Since Jara means “decay” or “aging” in Sanskrit, I speculate that Krishna actually died of old age, meditating in the forests. The Yadava tribes had reached such a state of cultural nadir due to their prosperity that they killed each other in large numbers in a drunken brawl. The Yadavas who survived the carnage dispersed and reached different parts of the Asian sub-continent. These events, albeit mythological, put things in perspective -- the mutability of all discrete things as expounded by the Indian philosophical school, Sankhya.
Sankhya is attributed to Kapila (mid-6th century BC), but it is more than likely that Sankhya had roots in the distant past, with several unknown seers contributing to its development. By the time of the Bhagavad Gita (2nd to 4th century BC antiquity), it is theorised that there were at least two Kapilas: One who wrote the original agnostic Sankhya Sutras, and the other whose theistic version of Sankhya is found in the Bhagavad Gita, the mythological conversation between Krishna and Arjuna.
Irrespective of the exact date of the founding of the Sankhya school, it is accepted to be the oldest school of Indian philosophical systems. Sankhya has greatly influenced the atheistic viewpoint of Jainism and the agnostic viewpoint of Buddhism. Although not openly acknowledged, it is apparent that the Upanishads are closer to Sankhya rather than the Vedas they are supposed to summarise. Note that neither ethics nor rituals are given any importance in the Sankhya school -- in direct contrast with the Vedic religion and in more contrast with any Western religion.
Sankhya is a school of philosophy which teaches discrimination of matter and energy, and of cause and effects. The word Sankhya itself means counting or discriminating. All creation is matter and energy. Matter and energy are neither created nor destroyed and are inert in isolation. Matter is governed by the three gunas (satva, rajas, tamas), which cancel out each other in the absence of energy. When matter and energy come together, consciousness is created. While energy tends to remain unchanged through this union, the balance of the three gunas, which govern matter, is upset. This results in matter undergoing change from its inert state to produce intellect, senses, and action. Intellect, senses, and action are in turn temporary. Matter eventually returns to its inert state.
Sankhya does not judge. The guna or quality of satva is illuminating and buoyant, rajas is of love and progress, tamas is the heavy-handed teacher (verse 13 of Sankhya Karika of Ishwara Krishna). All three gunas are required in the right mix to accomplish an outcome. In a corporate setting, I have translated this to create with freedom (satva), nurture with passion (rajas), and change with detachment (tamas). So also, in daily living, prescribing only sattvic ingredients is not, in my opinion, correct. The appropriate mental, food, and exercise choices should be based on the individual and his/her setting. Significant physical and mental harm is done by proponents of ‘sattvic is superior’ and that the rajasic and tamasic qualities are for lesser mortals.
Specifically, the goal of Sankhya is to attain the knowledge to discriminate between the self (energy), and the body (matter); the goal is to also understand the cause and effect relationships between the gunas, the intellect, the senses, actions, and final outcomes. This knowledge will liberate the self by virtue of knowing that it is the gunas that cause action, and the results of action are a systemic combination of a multitude of actions from various sources. So, the self develops a detachment from the results. The actions continue since the body is driven by the gunas into action. This is also Krishna’s message in the Bhagavad Gita.