“Before it explodes, a bomb is a single entity in which opposites coexist in given conditions. The explosion takes place only when a new condition, ignition, is present. An analogous situation arises in all those natural phenomena which finally assume the form of open conflict to resolve old contradictions and produce new things.”
On Contradiction (1937)
Original: (zh-CN) 炸弹在未爆炸的时候,是矛盾物因一定条件共居于一个统一体中的时候。待至新的条件(发火)出现,才发生了爆炸。自然界中一切到了最后要采取外部冲突形式去解决旧矛盾产生新事物的现象,都有与此相仿佛的情形。
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Mao Zedong 181
Chairman of the Central Committee of the Communist Party of… 1893–1976Related quotes

"Bluspels and Flalansferes: A Semantic Nightmare", Rehabilitations and Other Essays (1939)

Source: The Limits of State Action (1792), Ch. 16

On the Correct Handling of Contradictions Among the People
Original: (zh-CN) 马克思主义的哲学认为,对立统一规律是宇宙的根本规律。这个规律,不论在自然界、人类社会和人们的思想中,都是普遍存在的。矛盾着的对立面又统一,又斗争,由此推动事物的运动和变化。矛盾是普遍存在的,不过按事物的性质不同,矛盾的性质也就不同。对于任何一个具体的事物说来,对立的统一是有条件的、暂时的、过渡的,因而是相对的,对立的斗争则是绝对的。

Source: The Limits of State Action (1792), Ch. 16
Variant: The modern age did not so much invent new forms of migration as alter drastically the means and conditions of the old forms
Source: Europe on the Move: War and Population Changes, 1917-1947, 1948, p. 96 as cited in: Sarah Collinson (1999) Globalisation and the dynamics of international migration implications for the refugee regime http://www.unhcr.org/refworld/pdfid/4ff59b852.pdf. May 1999. p. 1

Source: The Causes of Evolution (1932), Ch. IV Natural Selection, pp. 104-106.
Context: Where natural selection slackens, new forms may arise which would not survive under more rigid competition, and many ultimately hardy combinations will thus have a chance of arising.... Thus the distinction between the principal mammalian orders seems to have arisen during an orgy of variation in the early Eocene which followed the doom of the great reptiles... Since that date mammalian evolution has been a slower affair, largely a progressive improvement of the types originally laid down in the Eocene.
Another possible mode of making rapid evolutionary jumps is by hybridisation.... hybridisation (where the hybrids are fertile) usually causes an epidemic of variation in the second generation which may include new and valuable types which could not have arisen within a species by slower evolution.