like a sport to them. The surveillance cameras, the sophisticated electronic police, the detection devices . . . the Vandals tried to beat them all.

And one of their main targets was the I.S.S.A.C. To these hostile people of the underground (the ''Resistance' as they called themselves), the thinking house was the sum total of everything they hated. It represented authority. It was the padded cell of modem man which had to be broken to pieces, so the world could be 'liberated' again.

As a result, the I.S.S.A.C's were improved. They were given defense systems. They were able to identify Vandals by smell, voice and sight. They could track them at night, using night-vision cameras and special sensors. They could stun and even kill any would-be threat to themselves.

The Vandals fell back, defeated. They had no hope of winning against these buildings. Day and night, continuously, the thinking houses were alert and awake. They never slept. Even while their human owners slept in temperature-controlled rooms, the houses were listening, sniffing, thinking, calculating, assessing, planning.

But then something happened which took all the scientists who had designed these perfect houses by surprise. It had once been theorized that if a computer system became part of several other computer systems, the total complexity of all the small systems joining forces and becoming one grand system might produce something new. The theory came, logically enough, from the example of the human brain. Within every human skull is a network of millions of nerve cells. On their own, each cell is pathetically small and feeble, and so small the unaided eye cannot even see it. A few nerve cells is hardly ‘intelligent’. But increase the number of cells, and put it with other clusters of cells and they can accomplish quite a lot. Combine the clusters with millions of other clusters, then connect them all up to a body and a living organism emerges. It seethed, according to the theory, that complexity was the only thing that lay at the heart of intelligence.

The I.S.S.A.C's were much the same as the nerve cells. In their ones and twos they were simply machines. They had highly developed computer systems and very useful sensoring devices, but they were still machines. Anyone could pull the plug out and the house would die.

But when the thinking houses were connected by radio-wave to the satellite systems, and when that system was connected with the telephone system and the air-traffic control system and the banking system and all the other world-wide systems, an amazing thing happened. The thinking houses became aware of themselves.