This is the age of machine. Machines are everywhere, in the fields, in the factory, in the home, In the street, in the city, in the country, everywhere. To fly, it is not necessary to have wings; there are machines. To swim under the sea, it is not necessary to have gills; there are machines. To kill our fellowmen in over-whelming numbers, there are machines. Petrol machines alone provide ten times more power than all human beings in the world. In the busiest countries, each individual has six hundred human slaves in his machines.
What are the consequences of this abnormal power? Before the war, it looked as though it might be possible, for the first time in history to provide food and clothing and shelter for the teaming population of the world-every man, woman and child. This would have been the greatest triumphs of science. And yet, if you remember, we saw the world crammed, full of food and people hungry. Today, the leaders are bare and millions, starving. That’s more begin to hum, are we going to see again more and more food, and people still hungry? For the goods, it makes the goods, but avoids the consequences.
According to the passage, which of the following is not necessary to fly?