A Deeper Question
There is still a deeper question. Why do variations occur'? Whether they are small or great, gradual or abrupt we cannot trace them to the influence of the environment. For types without variations seem to be just as well adapted as those with them. Darwin's view of chance variations is virtually a confession of his inability to explain the source of variations. Modifications and variations do not come singly but in complexes, involving many minor and consequential modifications and variations. Each single small variation is not independently selected. In other words, the organisms seem to 'vary' as a whole.
Bergson pointed out that the molluscs in the order of evolution proceed by steady steps to develop an eye, which resembles very much the eye developed by the independent line of vertebrates. How does it happen, he asked, that similar effects appear in different lines of evolution brought about by different means? How could the same small variations occur in two independent lines of evolution if they were purely accidental? According to Bergson, the two series must have been governed by a common vital impulse to this useful end. There is something more in evolution than merely mechanical urge. He is inclined to attribute a 'rudiment of choice' to the species which, travelling by different paths, reach the same goal. Given a new situation, the 'urge' (élan vital), common to all members, leads them to meet it by a new method. According to Bergson, it is the inner urge, or life force, or an upward drive, that incites the whole species in a definite direction. The striving of the organism is the creative effort to which evolution is due.