Thus, the dialectical view of development combats the theory of external causes, or of an external motive force,[4-390] advanced by metaphysics and vulgar evolutionism. It is evident that purely external causes can only give rise to mechanical motion, that is, to changes in scale or quantity, but cannot explain why things differ qualitatively in thousands of ways.[4-391] As a matter of fact, even mechanical motion under external force occurs through the internal contradictoriness of things. Simple growth in plants and animals is not only quantitative increase, it is at the same time the emergence of qualitative change; simple growth is likewise[4-392] the result of development arising from contradictions. Similarly, social development is due chiefly not to external but to internal causes. Countries with almost the same geographical and climatic conditions display great diversity and unevenness in their development. Moreover, great social changes may take place in one and the same country although its geography and climate remain unchanged, and this condition exists in many countries around the globe. Old Russian imperialism[4-393] changed into the socialist Soviet Union, and a purely feudal Japan, which had locked its doors against the world, changed into imperialist Japan, although no change occurred in the geography and climate of either country. Change was extremely limited in China with its several thousand year old feudal system, but recently there have been great changes, and is just now changing into a new China, liberated and free. Is it conceivable there are any differences between the geography and climate of China today and of several decades ago? It is quite evident, [p. 243] it is not due to external reasons but to internal reasons.[4-394] Changes[4-395]in nature are due chiefly to the development of the contradictions within things in nature. Changes in society are due[4-396] to the development of the internal contradictions in society, the contradiction between the productive forces and the relations of production, and the contradiction between classes,[4-397] and it is these that push society forward.[4-398] Does dialectics[4-399]exclude external causes? Not at all. The external causes are the condition of change and internal causes are the basis of change, the external causes become operative through internal causes. In a suitable temperature an egg changes into a chicken, but no temperature can change a stone into a chicken, because the basis of the internal causes is different. The pressure of imperialism accelerated change in Chinese society, and these changes were effected through the inner regularities