Injunctions like 'Do not cause death', 'Do not steal', 'Speak the truth' (satyam vada), Act righteously (dharmam cara) etc. are of this kind. These injunctions or courses of conduct are definitely laid down in the Manu-Smrti, and other Smrtis, and in the Upanisads. But as man is a rational animal, he is not satisfied with such didactic injunctions, and he naturally feels a desire to understand the true reason why they were laid down ; and he naturally thinks over and finds out the eternal and fundamental principle at the bottom of these rules of conduct. Going to the bottom of worldly morality in this way, and finding out the underlying fundamental principles, is the purpose of PHILOSOPHY (Sastra); and merely putting together and mentioning the rules, is known as AGARA- SAMGRAHA.
The code of rules of conduct (acara-samgraha) relating to the Path of Action is to be found in the Smrti texts; and the Bhagavadgita contains a conversational or Pauranika, but philosophical (sastriya) disquisition on the fundamental principles of that code. Therefore, it is more proper to say that the subject-matter of exposition in the Gita is THE SCIENCE OF KARMA-YOGA (Karma-Yoga-Sastra), instead of saying that it is KARMA-YOGA; and this word, that is, SCIENCE OF YOGA (Yoga-Sastra) has been used in the Gita in the concluding portion of every chapter showing the end of the chapter. This Science of Karma-Yoga in the Gita has been called the Science of Proper Conduct (sadvartana), the Science of Good Behaviour (sadacara), Philosophy of Ethics, Critique of Ethics, Elements of Ethics, the Science of Duty, the Discernment of Right and Wrong, or the Science of Sociology, by Western philosophers, who either do not believe in the life after death, or consider it as inferior.
These are merely Materialistic names ; and their way of criticising is also a purely Materialistic way. Therefore, the majority of the persons who have read the books of such Western writers think that Morality or Ethics has not been dealt with in any work in Sanskrit literature. The most profound philosophy in India is the Vedanta philosophy ; and if one considers our modern Vedanta works, they are seen to be principally indifferent about worldly affairs. Then, how can we find in them any consideration of Karma-Yoga or of Ethics ? This subject-matter cannot be dealt with in books on Grammar, or on Logic ; and in the Smrti texts, one cannot find anything more- than a code of religious precepts.