In ordinary life, we tend to think of "peace" as essentially "a lack of conflict." As a nation, if we're not at war, it's a...
'Perpetual' in the literal sense, means to the end of one’s life, after death, and eternity.
'Spreading themselves on the earth,' as in Genesis 8:17, signifies the internal self operating on the external.
'Middle' denotes what is primary, principal, or inmost.