I think in the context of the song, equating "will" with "instinct" makes a lot of sense. Will is synonymous with desire, and our desires are driven by our needs to reproduce, live comfortably, eat, sleep, etc. Humans have the ability to break away from our instincts which is unique to the species, but most people never do that. Even though we have freedom of choice, we generally neglect choices that differ from our most base instincts. So looking at the big picture and comparing this to universal situations is certainly valid, but I don't find it necessary. The point, much like the point of "Right in Two" is that humans neglect their ability to help each other and to behave morally and instead cling to instincts which are often destructive.

I also believe that the line "Pure as we begin" is somewhat sarcastic or at least melancholic and stands in direct contrast to "Move by will alone." It is true that we begin pure and without influence, but we're bound to be enslaved by our own instincts sooner or later, as well as the nurturing of the society we live in.

In one sentence, the song is about human rejection of morality.