Vegetables also have consciousness, but that consciousness is very, very little. Humans have the highest consciousness. The next is big animals, and then smaller ones. Therefore, killing humans are the biggest crime. The greater consciousness of beings you kill, the greater karma and sin you will have. Eighty or ninety percent of the plants or vegetables is made up of water and with very little consciousness. They will not suffer so much as humans, big and small animals, therefore, one does not commit so much sin by eating vegetables.
Why can we eat vegetables? First, some plants like to be eaten by us so that they can evolve to a level a little bit higher. Second, after being cut and eaten by us, the plants can grow new leaves. The more we take, the more they will grow. The animals, however, will become nothing after being killed. That's why we know eating vegetarian is OK, but eating animals is not. Eating plants also has karma; even breathing has karma too, because there are numerous microorganisms in the air. We are already creating karmas without doing anything. We have karma already when we were born. That's why we need to practice spiritually, meditate and practice Quan Yin Method every day. Then we'll have no karma.