LIMITS OF PHYSICAL KNOWLEDGE 259 



down thought as an illusion — some perverse interpreta- 

 tion of the interplay of the physical entities that he has 

 found. Or if he sees the folly of calling the most un- 

 doubted element of our experience an illusion, he will 

 have to face the tremendous question, How can this col- 

 lection of ordinary atoms be a thinking machine? But 

 what knowledge have we of the nature of atoms which 

 renders it at all incongruous that they should constitute 

 a thinking object? The Victorian physicist felt that he 

 knew just what he was talking about when he used such 

 terms as matter and atoms. Atoms were tiny billiard 

 balls, a crisp statement that was supposed to tell you 

 all about their nature in a way which could never be 

 achieved for transcendental things like consciousness, 

 beauty or humour. But now we realise that science has 

 nothing to say as to the intrinsic nature of the atom. The 

 physical atom is, like everything else in physics, a 

 schedule of pointer readings. The schedule is, we agree, 

 attached to some unknown background. Why not then 

 attach it to something of spiritual nature of which a 

 prominent characteristic is thought. It seems rather silly 

 to prefer to attach it to something of a so-called "con- 

 crete" nature inconsistent with thought, and then to 

 wonder where the thought comes from. We have dis- 

 missed all preconception as to the background of our 

 pointer readings, and for the most part we can discover 

 nothing as to its nature. But in one case — namely, for 

 the pointer readings of my own brain — I have an in- 

 sight which is not limited to the evidence of the pointer 

 readings. That insight shows that they are attached to 

 a background of consciousness. Although I may expect 

 that the background of other pointer readings in physics 

 is of a nature continuous with that revealed to me in this 

 particular case, I do not suppose that it always has the 



