ADDRESS. 5 
see. It must always be profoundly interesting to the mind of man 
to trace successive cause and effect in the chain of events which make 
up the history of the earth and all that lives on it, and to speculate 
on the origin and future fate of animals, and of planets, suns, and 
stars. I shall try, then, to set forth in my address some of the attempts 
which have been made to formulate Evolutionary speculation. This 
choice of a subject has moreover been almost forced on me by the scope 
of my own scientific work, and it is, I think, justified by the name 
which I bear. It will be my fault and your misfortune if I fail to 
convey to you some part of the interest which is naturally inherent in 
such researches. 
The man who propounds a theory of evolution is attempting to recon- 
struct the history of the past by means of the circumstantial evidence 
afforded by the present. The historian of man, on the other hand, has 
the advantage over the evolutionist in that he has the written records of 
the past on which to rely. The discrimination of the truth from amongst 
discordant records is frequently a work demanding the highest qualities 
of judgment ; yet when this end is attained it remains for the historian 
to convert the arid skeleton of facts into a living whole by clothing it 
with the flesh of human motives and impulses. For this part of his task 
he needs much of that power of entering into the spirit of other men’s 
lives which goes to the making of a poet. Thus the historian should 
possess not only the patience of the man of science in the analysis of facts, 
but also the imagination of the poet to grasp what the facts have meant. 
Such a combination is rarely to be found in equal perfection on both 
sides, and it would not be hard to analyse the works of great historians 
so as to see which quality was predominant in each of them. 
The evolutionist is spared the surpassing difficulty of the human 
element, yet he also needs imagination, although of a different character 
from that of the historian. In its lowest form his imagination is that of 
the detective who reconstructs the story of a crime; in its highest it 
demands the power of breaking loose from all the trammels of convention 
and education, and of imagining something which has never occurred to 
the mind of man before. In every case the evolutionist must form a 
theory for the facts before him, and the great theorist is only to be dis- 
tinguished from the fantastic fool by the sobriety of his judgment—a 
distinction, however, sufficient to make one rare and the other only too 
common. 
The test of a scientific theory lies in the number of facts which it 
groups into a connected whole ; it ought besides to be fruitful in pointing 
the way to the discovery and co-ordination of new and previously un 
suspected facts. Thus a good theory is in effect a cyclopzdia of knowledge, 
susceptible of indefinite extension by the addition of supplementary 
volumes. 
Hardly any theory is all true, and many are not all false. A 
theory may be essentially at fault and yet point the way to truth 
