By the middle of the seventeenth century it had come to be understood that the world was enclosed in a sea of air, much as the greater part of it was covered by water. A scientist of the period, Francesco Lana, contended that a lighter-than-air ship could float upon this sea, and he suggested how such a ship might be built. He was unable to put his invention to a practical test, but he saw only one reason why it might not work:

". . . that God will never suffer this Invention to take effect, because of the many consequencies which may disturb the Civil Government of men. For who sees not, that no City can be secure against attack, since our Ship may at any time be placed directly over it, and descending down may discharge Souldiers; the same would happen to private Houses, and Ships on the Sea: for our Ship descending out of the Air to the sails of Sea-Ships, it may cut their Ropes, yea without descending by casting Grapples it may over-set them, kill their men, burn their Ships by artificial Fire works and Fire-balls. And this they may do not only to Ships but to great Buildings, Castles, Cities, with such security that they which cast these things down from a height out of Gun-shot, cannot on the other side be offended by those below."

Lana's reservation was groundless. He had predicted modern air warfare in surprisingly accurate detail—with its paratroopers and its strafing and bombing. Contrary to his expectation, God has suffered his invention to take effect. And so has Man.

• B. F. Skinner, "Science and Human Behavior"