Aptly, Indian philosophy compares a thought to a seed: very tiny, but it can grow into a huge, deep-rooted, wide-spreading tree. I have seen places where a seed in a crack of a pavement grew into a tree that tore up the sidewalk. It is difficult to remove such a tree, and terribly difficult to undo the effects of a lifetime of negative thinking, which can extend into many other people’s lives. But it can be done, and the purpose of the Gita is to show how.
