Thought fusion was an illusion. A greater power would of necessity be unknown. Fusion might qualify as some part of that definition. I don't know.
The known ranges from sub atomic to universal through molecular, planetary, galactic each bound by energy that seems related to motion. A greater power would be that of which the known is part. It is unknown and vulnerable to hypothetical definition. The hypothetical definition of 'greater power' could form the basis for a broad system of belief that could describe the role of human life as a part of a balanced cosmic system .
Does this help ?
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No, fusion isn't an illusion.
In fact, there's a respectable and venerable fusion reaction blazing about 149 million km from us right now.
But...of course, you're referring to terrestrial fusion. I wouldn't call it an illusion so much as very, very tough to sustain -- and even if sustained, it's hella radioactive. Which isn't a bad thing, just requires mature handling.
Here's where the curious can go to get an overview:
<http://en.wikipedia.org/wiki/Thermonuclear_fusion>
Re: 'greater power'...
There are plenty of belief systems which "describe the role of human life as a part of a balanced cosmic system". Trouble is, competing schools of adherents never agree on the particulars and eventually get to smashing each other on the head with chairs, hammers, surface to surface missiles and microwave disrupters. Deadly! And dull.
Better, I think, to focus our 'green' musings on de-carbonization's social and technical requirements and leave the cosmic re-alignment quest for weekends lubricated with Belgian ale.
.d.