Every mental state exists for a purpose; to understand it, we must ask what function it serves in the broader system of behavior.
每种心理状态都有其存在的目的；要理解它，我们必须询问它在更广泛的行为系统中发挥什么功能。
The solution of a problem appears suddenly and is not approached by a gradual, step-by-step procedure.
The stone industry must embrace sustainability to survive in the long run.
知识是解锁心灵之门的钥匙。