"Witches are horrified of computers.  Machines made in the image of a human mind but without a human soul," he said, going down the far side of the rubble, into the large tunnel.  "Some said that the Old People's thinking machines are what destroyed them.  That the cold reasoning of their thinking machines calculated that humanity's destruction was perfectly reasonable.  They say it like it was a bad thing, though they also believe that it was necessary to diminish human civilization to have any chance of reviving the natural order of the world.  But if the computers made the same calculation, it becomes bad?  I don't get souls."<br/><br/>Inside, it was large enough to run two trains abreast, and there were still iron rails on the ground, pitted with rust.  The air was dank, smelling of mildew and concrete.  The air was still, there was the sound of dripping water from all around.  It was damp and cold, the kind that got into your bones.<br/><br/>There were also faraway scents - the ozone of electricity, human scents, and animal ones, too, but mixed with the further reek of heavy metals like sucking on a battery, something acidic, the stink of burning things.  There was life down there, but death, too.<br/><br/>When she reached out through the link, he nodded and communicated without words that they should move on.  It wasn't safe at the openings into the underworld.  Things came and went by that route and it would be best to avoid them.