So he proceeds to portray with a wealth of analogy and brilliance of style, more akin to the language of a poet than a philosopher, the stupendous drama of Evolution, the mystery of being, the wonders of life. He makes the great fact of life his starting point. Is life susceptible to definition? We feel that, by the very nature of the case, it is not. A definition is an intellectual operation, while life is wider, richer, more fundamental than intellect. Indeed Bergson shows us that intellect is only one of the manifestations or adaptations of life in its progress. To define life, being strictly impossible, Bergson attempts to describe it. He would have us picture it as a great current emerging from some central point, radiating in all directions, but diverted into eddies and backwaters. Life is an original impetus, une poussee formidable, not the mere heading affixed to a class of objects which live. We must not speak any longer of life in general as an abstraction or a category in which we may place all living beings. Life, or the vital impulse, consists in a demand for creation, we might almost say "a will to create." It appears to be a current passing from one germ to another through the medium of a developed organism, "an internal push that has carried life by more and more complex forms, to higher and higher destinies." It is a dynamic continuity, a continuity of qualitative progress, a duration which leaves its bite on things. [Footnote: For these descriptions of life, see Creative Evolution, pp. 27-29 and 93-94 (Fr. pp. 28-30 and 95-96).] We shall be absolutely wrong, however, if we attempt to view the evolutionary process as progressive in a straight line. The facts contradict such a facile and shallow view. Some of the stock phrases of the earlier writers on Evolution were: "adaptation to environment," "selection" and "variation," and a grave problem was presented by this last. How are we to account for the variations of living beings, together with the persistence of their type? Herein lies the problem of the origin of species. Three different solutions have been put forward. There is the "Neo-Darwinian" view which attributes variation to the differences inherent in the germ borne by the individual, and not to the experience or behaviour of the individual in the course of his existence. Then there is the theory known as "Orthogenesis" which maintains that there is a continual changing in a definite direction from generation to generation. Thirdly, there is the "Neo-Lamarckian" theory which attributes the cause of variation to the conscious effort of the individual, an effort passed on to descendants. [Footnote: Concerning Lamarck (1744-1829) Bergson remarks in La Philosophie (1915) that without diminishing Darwin's merit Lamarck is to be regarded as the founder of evolutionary biology.] Now each one of these theories explains a certain group of facts, of a limited kind, but two difficulties confront them.