Illustrations of exchanges of stability 547 
homologous considerations in other fields of thought}, and I shall pass 
on thence to illustrations which will teach us something of the 
evolution of stellar systems. 
States or governments are organised schemes of action amongst 
groups of men, and they belong to various types to which generic 
names, such as autocracy, aristocracy or democracy, are somewhat 
loosely applied. A definite type of government corresponds to one of 
our types of motion, and while retaining its type it undergoes a slow 
change as the civilisation and character of the people change, and as 
the relationship of the nation to other nations changes. In the 
language used before, the government belongs to a family, and as 
time advances we proceed through the successive members of the 
family. A government possesses a certain degree of stability—hardly 
measurable in numbers however—to resist disintegrating influences 
such as may arise from wars, famines, and internal dissensions. This 
stability gradually rises to a maximum and gradually declines. The 
degree of stability at any epoch will depend on the fitness of some 
leading feature of the government to suit the slowly altering circum- 
stances, and that feature corresponds to the characteristic denoted by 
a in the physical problem. A time at length arrives when the 
stability vanishes, and the slightest shock will overturn the govern- 
ment. At this stage we have reached the crisis of a point of 
bifurcation, and there will then be some circumstance, apparently 
quite insignificant and almost unnoticed, which is such as to prevent 
the occurrence of anarchy. This circumstance or condition is what 
we typified as 6. Insignificant although it may seem, it has started 
the government on a new career of stability by imparting to it a new 
type. It grows in importance, the form of government becomes 
obviously different, and its stability increases. Then in its turn this 
newly acquired stability declines, and we pass on to a new crisis or 
revolution. There is thus a series of “points of bifurcation” in 
history at which the continuity of political history is maintained by 
means of changes in the type of government. These ideas seem, to 
me at least, to give a true account of the history of states, and I 
contend that it is no mere fanciful analogy but a true homology, 
when in both realms of thought—the physical and the political—we 
perceive the existence of forms of bifurcation and of exchanges of 
stability. 
1 I considered this subject in my Presidential address to the British Association in 
1905, Report of the 75th Meeting of the British Assoc. (S. Africa, 1905), London, 1906, p. 3. 
Some reviewers treated my speculations as fanciful, but as I believe that this was due 
generally to misapprehension, and as I hold that homologous considerations as to stability 
and instability are really applicable to evolution of all sorts, I have thought it well to 
return to the subject in the present paper. 
35—2 
