416 The Evolution of Scientific Knowledge. [July, 
A hypothetical example of the simplest possible kind will 
not here be out of place. Take a tribe of savages in the 
pre-social stage. Each individual does for himself all that 
he wants done : he cuts his own bow, makes his own arrows, 
and shoots for himself the wild creatures from which he has 
himself to prepare food, and perhaps clothing. Now let 
Evolution come into play. Differentiation sets in. 1 here 
is an incipient division of labour. One individual devotes 
himself to the making of bows and arrows on the under- 
standing that they whom he supplies shall procure him food 
and clothing ; another dresses the food or the skins on simi- 
lar terms ; and so on. It is needless to elaborate this 
example ; for without elaboration it is clear that the indivi- 
duals of a tribe so far evolved have become more different, 
and at the same time more dependent on each other ; while 
the tribe itself has been converted into a more definite, 
complex whole. 
Such being, therefore, the law of Evolution, I propose in 
this paper to apply it to the history of Science. I shall en- 
deavour to show that the advance in complexity, definite- 
ness, and integration, which constitutes Evolution, is seen 
not less clearly in our knowledge of phenomena than in the 
phenomena themselves. It matters not, I believe, to which 
branch of Science we turn our attention; all tell the same 
tale. Definiteness of observation, complexity of subject 
matter, interdependence of phenomena, comprehensiveness 
of generalisation— all these advance hand in hand. The 
history of science is the history of an evolution, and the 
Law of Evolution is the outcome of that evolution. 
At the outset, however, an objection may be raised to this 
application of a physical law to the products and processes 
of the mind. And to those who see no connection between 
consciousness and the vibration of brain-molecules, who 
recognise no physical basis of mind, the objection is probably 
insuperable. But while the faCt cannot be too frequently 
insisted upon, that we are utterly and completely unable to 
conceive how the vibrations, decompositions, or isomeric 
changes of grey nitrogenous matter may be accompanied by 
the phenomena of conscious thought; while we must honestly 
confess that this is, and probably ever must be, an inscrutable 
mystery; still we seem forced, by the balance of scientific 
evidence, to infer that there does exist a definite connexion 
between what we characteristically call brain power and 
thought. And if this be so, then it is evident that the 
evolution of scientific knowledge is but the sign of the evo- 
lution of one portion of the individual and social organisation. 
