The probability of a response is determined by its reinforcement history.

The happiest people are those who have found purpose while still appreciating life's simple joys.

国家间的合作是解决公海过度捕捞问题的关键。

生活不是等待暴风雨过去，而是学会在雨中跳舞。

The state, therefore, has not existed from all eternity. There have been societies that did without it, that had no notion of the state or state power. At a certain stage of economic development, which was necessarily bound up with the split of society into classes, the state became a necessity.