What is the new entity? Gaia is a conscious planet. Everything, from blades of grass, to food animals, to humans, is part of a collective consciousness and plays a role in determining the course of the planet's civilization. Though it predates both Foundations, Gaia has enveloped itself in secrecy until now. The Gaians have decided a decision has to be made. Whither galactic civilization? They believe their choice — a conscious galaxy based on their planet, called Galatea — is the best plan for the future. However, the Seldon Plan is in the way.

From Asimov's perspective, there are three options:

~ The First Foundation, which is very advanced in technology, and catching up in regard to mind control, can declare a new empire. The declaration would be 500 hundred years ahead of the Seldon Plan's intentions, but the new empire would probably be as sustainable as the previous empire.

~The Second Foundation can continue its stewardship of the Seldon Plan. A new empire will emerge in 500 years, as planned. It will be dominated by the Speakers, leaders of the Seconds. The benefit is that the violence of previous human societies will be avoidable. The expert mind control of the Second Foundation will guarantee a peaceful future.

~ All the galaxy can accept Gaia as a model. Eventually, all life will be an integrated whole. Issues of conflict and violence will be resolved as humans evolve beyond such behavior under Gaia's influence.

It is probably a measure of my distance from Asimov's thinking that my response to the three options was 'none of the above.' It seems to me that he is again imposing his views as if they are the only ones available. All three of his options rely on a domineering elite controlling not just countries, but planets, even the galaxy. My inclination is to favor a diversity of solutions to the problems of human nature, including war. Perhaps some planets would form an alliance before the end of the Seldon Plan. Maybe the Second Foundation would control some planets, but not others. It seems entirely possible that societies with pacifist inclinations would be amenable to knowingly joining Gaia.

A plan for the future of the galaxy is chosen through typical Asimovian sleight-of-hand. It is as if having actions occur openly is taboo to him. There must be subterfuge. Though I have described the possibilities above, I've decided against an actual spoiler. Read Foundation's Edge to learn what the outcome is.

Reasonably related

The first three books in the Foundation cycle were written decades before the last three. I reviewed them previously. There also an addendum to the cycle, Foundation and Earth.

Note: My blog is Mac-a-ro-nies.