been more or less directly involved in those departments of Science and Philosophy which have during this period received the largest share of popular attention.
Perhaps the greatest impetus was given to the spread of the doctrine about fourteen years ago, by the publication of Mr. Darwin's now celebrated "Origin of Species." This volume has been followed by quite a library of works and memoirs on the same subject—partly scientific and partly popular. From about the same date also, Mr. Herbert Spencer has been engaged in systematically elaborating the principles of an all-comprehensive Evolution Philosophy, and the results of his genius and labor are now undoubtedly influencing the thoughts of a rapidly-widening circle of readers. Both in this country and abroad, the doctrine of Evolution is gradually but surely gaining ground among the most reflective; and, although many other writers have been more or less influential in determining this result, it has been in the main brought about by the two above mentioned.
Evolution implies continuity and uniformity. It teaches us to look upon events of all kinds as the products of continuously-operating causes—it recognizes no sudden breaks or causeless stoppages in the sequence of natural phenomena. It equally implies that natural events do not vary spontaneously. It is a philosophy which deals with natural phenomena in their widest sense; it embraces both the present and the far distant past. It seeks to assure us that the properties and tendencies now manifest in our surrounding world of things are in all respects similar to those which have existed in the past. Without a basis of this kind, the Evolution hypothesis would be a mere idle dream. Uniformity is for it an all-pervading necessity. Starting from facts of daily observation and from scientific experiments, the properties and tendencies of things are noted and grouped; while philosophers, using the knowledge thus gained, seek to trace back the progress of events and show how this complex world has gradually been derived from a world of more and more simple composition. We are taken back in imagination even much farther. We are referred to a primal haze or nebula––as the gigantic germ of a future Universe. This was the conception of Laplace.
But whether we follow the philosopher in his bold speculations concerning the past, or listen to the biologist making his predictions concerning the future stages which the germ of a given animal will pass through in the progress of its evolution—in each case the "uniformity of Nature" is tacitly assumed. This assumption underlies almost all our thoughts and actions, even in every-day life. And, without such a belief in the Uniformity of Nature, science would be impossible—the very idea of it, in fact, could never have arisen. In its absence we could neither fathom the past nor illumine the future. As Mr. Mill said[1]—"Were we to suppose (what it is perfectly possi-
- ↑ "System of Logic," sixth edition, vol. ii., p. 98.
