228 THE NEW QUANTUM THEORY 



inconsistency in supposing it to have been under the 

 surveillance of relays of watchers whilst we were asleep. 

 But it is otherwise with an electron. At certain times, 

 viz. when it is interacting with a quantum, it might be 

 detected by one of our watchers; but between whiles it 

 virtually disappears from the physical world, having no 

 interaction with it. We might arm our observers with 

 flash-lamps to keep a more continuous watch on its 

 doings; but the trouble is that under the flashlight it 

 will not go on doing what it was doing in the dark. 

 There is a fundamental inconsistency in conceiving the 

 microscopic structure of the physical world to be under 

 continuous survey because the surveillance would itself 

 wreck the whole machine. 



I expect that at first this will sound to you like a 

 merely dialectical difficulty. But there is much more in 

 it than that. The deliberate frustration of our efforts to 

 bring knowledge of the microscopic world into orderly 

 plan, is a strong hint to alter the plan. 



It means that we have been aiming at a false ideal of 

 a complete description of the world. There has not yet 

 been time to make serious search for a new epistemology 

 adapted to these conditions. It has become doubtful 

 whether it will ever be possible to construct a physical 

 world solely out of the knowable — the guiding principle 

 in our macroscopic theories. If it is possible, it involves 

 a great upheaval of the present foundations. It seems 

 more likely that we must be content to admit a mixture 

 of the knowable and unknowable. This means a denial 

 of determinism, because the data required for a pre- 

 diction of the future will include the unknowable ele- 

 ments of the past. I think it was Heisenberg who said, 

 u The question whether from a complete knowledge of 

 the past we can predict the future, does not arise because 



