An Existential Conflict And A Creative Tension

In the first part of Poul Anderson's Psychotechnic History, there is an existential conflict between the Un-Men and the "protean enemy" whereas, in the second half of this future history series, the conflict between the order-preserving Coordination Service and the unintegrated Nomads is more like a creative tension. Civilization has advanced to a stabler level. Coordinators and Nomads are a perfect thesis and antithesis and the perfect synthesis is provided when some Cordies join the Nomads, bringing with them knowledge and expertise that will survive through the Third Dark Ages and inform later civilizations. 

If "The Chapter Ends" is to be believed, then the next level of thesis and antithesis is between human and Hulduvian ways of controlling cosmic energy and this conflict is resolved by agreeing to divide the galaxy between oxygen- and hydrogen-breathers.