( Or Sacrifice. ?)
This is perhaps one of the least understood but most controversial topics in Vedic philosophy. In fact I would not even use the word sacrifice, but the limitations of English language do not permit a one word substitute for the concept of 'yajna'. Moreover, English translations of the Vedic Texts by Western scholars imply that Yajna is a sacrifice and the connotation is generally negative - in the form of some inane ritual or some kind of animal sacrifice and this straight substitute has been popularised over the last 300 years or so. In fact they (Western Vedic scholars) wouldn't be far off from the truth given that Hindu ritualists also associate yajna with physical sacrifices.
However, Yajna is a sophisticated and subtle abstraction. Although in some contexts it might loosely imply sacrificial action, it is in reality much more than that. The Vedic texts were written by some of the most mentally and spiritually evolved beings of their times, not by some intellectually inferior shephard or village bumkin as suggested by many Western translators. The thought construct associated with a yajna is much more refined and subtle than its manifestation in the form of some sort of ritual or sacrifice. The originators realized and comprehended (through rational and spiritual mechanisms) 'yajna' and were at no fault when they conceived of a suitable thought construct to capture the essence of this realization. Subsequently various set of people over the last two millenia have interpreted it differently and invariably most of these interpretations veer towards some sacrifice or ritual. However, in this text I will use not use yajna and sacrifice interchangeably.
At the highest level, yajna is a thought construct founded in singularity but manifested in duality. What I mean by this a yajna always has two legs to it - roughly put a subject and an object. Although in some case the subject and object might apparently be the same, we should note that they are actually distinct in that the object might actually be a differnt manifestation of the subject as conceived through the frame of reference known as Maya. At another level yajna is an universal causality principle bounded in an action-reaction framework. Simply put, it is an acceptance of the notion that to get something, something else has to be given up. Let me see if I can explain this idea in a lucid manner.
The Vedic seers had understood that the entire Universe (as manifested through Maya) is bounded by some very fixed set of laws. The deeper they delved, the more they realized that each of these universal phenomena could be explained by one thought construct - that of 'Yajna'. Be it the creation of a star, or the death of a person, or the cyclical nature of seasons or the way our mind works - the only common thread that ran through all these varied events was 'Yajna' or sacrifice.
According to the Vedic rishis, life itself is the biggest 'yajna'. For someone to live, someone or something must die. At a macroscopic level, man kills for food - thus food now becomes a yajna or sacrifice. When a man eats rice, he is killing millions of sources of life by consuming the seeds. Any food that a man consumes is a sacrifice. Sacrifice or yajna is inevitable and inextricably linked with Maya; there is no escaping it. Even when somebody thinks that he eats only leaves or fruits which have fallen from the tree or drinks only water - even then he is peroming 'yajna'. He is sacrificing millions of microscopic beings that reside in water or grow on the leaves. Yajna is everywhere. As long as we are in the confines of Maya, there is no avoidance of Yajna. With every breath that we inhale and exhale millions of microscopic organisms. With every touch, with every movement, every look, every smell - we sacrifice something to get the sense feelings. In fact, our entire existence is based on 'yajna' at all levels starting from the macroscopic to microscopic. However, with proper Yoga of breathing or mind or knowledge, we can minimize the magnitude of harm caused to other beings - but we can never ever stop it. We have to accept this Truth as long as we talk about our Universe as we see it through our frame of refernce (3 dimensions, 5 senses) or through Maya.
Yajna might happen at 3 levels - physical, mental or intellectual and spiritual level. At a physical level it involves life, death, food, creation of planets, waves in an ocean and all other physical phenomenon. At a mental level, yajna is the sacrifice of less imprtant thoughts to allow the more important thoughts to flourish. At a spiritual level, yajna involves giving up the concept of the Self as Body in order to realize the Self as the One. Voluntarily or involuntarily, Yajna happens all the time. The Vedic texts talk about it in details. Bhagawad Gita touches upon various aspects of Yajna and it is dealt with in almost every chapter. Yajna is a central aspect of the Vedantic thoughts and needs to be appreciated at all the 3 levels.
It is only at the physical level that yajna takes the form of a sacrifice or ritual when we humans attribute it's literal meaning to the term and it is this idea that has given rise to the notion of a sacrifice - be it a small ritual in someone's home or a highly elaborate and complex one involving various stakeholders.
As we can see, Yajna goes much deeper than what is normally assumed. It is not merely some sort of primitive practice of a culturally backward race - at least the principle and intentions of 'yajna' are definitely much more refined and subtle than even the most refined of modern thoughts - it is in the (mis-)interpretations (past and present) that the problem arises.