APPENDIX. 
DISCUSSION ON 
THE EVOLUTION OF THE UNIVERSE. 
(Sir James Jeans, F.R.S.; Prof. E. A. Mitnez, M.B.E., F.R.S.; Prof. 
W. ve Srirrer; Prof. Sir, A. S. Eppryeton, F.R.S.; Prof. R. A. 
Mriu1kan; Rt. Rev. the Lorp BisHop or BirmincHam, F.R.S. ; 
Gen. the Rt. Hon. J. C. Smuts, P.C.,C.H., F.R.S.; M. ABBE 
Lemaitre ; Sir Ottver Lopes, F.R.S.) 
Held in Section A (Mathematical and Physical Sciences) 
-on Tuesday, September 29, 1931. 
Sir JamES JEANS, F.R.S. 
With so large a subject, and so short a time, I can only hope to sketch 
out a sort of skeleton in its barest outlines, leaving it for the other speakers 
to fill in details according to their individual interests and opinions. 
We are, of course, discussing only the physical universe. Here strict 
determinism reigns, because even if there is no determinism in the 
behaviour of individual atoms, there are so many atoms in even the 
tiniest bit of matter that we may take an average. The laws of probability 
provide something which is, for our present purpose, equivalent to a strict 
physical determinism. 
It follows that the final state of the universe is inherent in the present 
state, just as this present state was inherent in the universe at its creation. 
The physical universe never has any choice—it must inevitably move 
along a single road to a predestined end. What we are calling evolution 
is like the rolling of a train along a single-track line, with no junctions of 
any kind. 
The various possible lines of development for the universe are like an 
enormous number of single-track lines. We can imagine these running 
through a diagram in which all possible configurations of the universe are 
mapped out, just as all points in England are mapped out in an ordinary 
map. As we do not know which track we are on, it is futile to discuss at 
what particular spot it ends. But we may be able to discover in what 
kind of country it ends, and this is really the information we want. 
Imagine that we suddenly waken up from a state of unconsciousness 
to discover we are on a British railway. We have no means of knowing 
where our journey will end. Yet if we have a physical map of Great 
Britain with us we may notice that only a few hundred acres out of 
55 million lie more than 4,000 feet above sea-level. Although we cannot 
say where our journey will end, there are obviously very long odds that 
it will end at less than 4,000 feet above sea level. If a barometer in our 
