When man's ambition expanded to fill the solar system, his technology expanded to take him as far as he wanted to go. Technology went on expanding. So did man's ambitions. But there was a danger only dimly suspected, and only poorly comprehended when it began to make itself felt. It was that man's ambition would outleap his imagination; that his technology would outstrip his emotional capacity. It might be that it was just too big, the universe. That there was just too much to of nothing for man to bear... Fix-up novel made up of the following previously published stories:

• Making Titan, as Chapter I, "Making Titan, 2500"
• A Triptych, as Chapter II, "Some Headlines in the Void, 1968"
• Conquest, as Chapter VI, "The Conquest of Conquistadores, 2423"
• Terminus Est, as Chapter VII, "An Interval In the Adventure, 1999"
• Pacem Est, originally written with Kris Neville, but rewritten as Chapter X, "The Martian Campaign, 2124"
• Elephants as Chapter XIII, "After Titan, 2500+"
• How I Take Their Measure, as "Interview with an Astronaut, 2008", part of Chapter XIV