Why be a Vegetarian?

All the energy in this world comes from the Sun. This energy is then absorbed by different beings in different ways. Plants catch this energy directly from the Sun and by the process of photosynthesis absorb this energy and grow. I believe and have heard that there are saints who can do the same - absorb energy directly from the sun without having to eat any food. And then there are animals (those that are lower in the food chain), that eat the plants and get the energy from the Sun, through plants. Vegetarians also get their energy from the Sun, through plants. Animals that are higher in the food chain and non-vegetarians eat animals and get the energy from the Sun through plants through other animals.

Now, the direct energy from the Sun is of the purest nature. As this energy passes through plants and through animals, it accumulates some of the nature of the plants and animals through which it passes, and so it become gradually impure.

Our thoughts and actions and our nature is determined by the food we consume, i.e. the energy we consume. The thoughts and actions of someone who always consumes the pure form of energy will be pure, while the thoughts and actions of someone who consumes impure energy will be impure. Now, what is pure and what is impure?

Our goal in life is to be of service to others, to put others' needs above our own needs. This concept is present in almost every religion - that is why giving alms, charity, donation etc. are an integral part of religions. In SriViashnavism also the same concept is upheld formeost - Bhagavat kainkaryam (service to God) and Bhaagavatha kainkaryam (service to fellow beings, not just human beings but all beings) is the ultimate goal. The sole purpose of Madhurakavi Azhvar was to reinforce Bhaagavatha kainkaryam as the ultimate goal. So now, with service to others and putting others' needs above our own needs being the ultimate goal, any action or thought that is aligned with the ultimate goal is pure and any other thought that is not aligned with the ultimate goal is impure. i.e. If a thought or action is for servicing others and putting others' needs above our own needs, it is a pure thought or action. Any other thought or action is impure.

Since the purity of the energy we consume controls the purity of our thought or actions, it is better to consume as pure a form of energy as we can. Directly consuming energy from the sun is beyond our reach for most of us. So, the best we can do is be vegetarian, so our thoughts and actions will be directed towards servicing others and putting others' needs above our own. This is why Thiruvalluvar in his Thirukkural says:
"Than Oon perukkarkuth thaan piridhu Oon unbaan, enganam aalum Arul",
"தன் ஊன் பெருக்கற்குத் தான் பிறிது ஊன் உண்பான் எங்ஙனம் ஆளும் அருள்"
meaning, "If one eats anothers' body in order to build ones own body, he will not have the quality Arul". "Arul" is compassion towards fellow beings, putting others' needs above our own.