PAC学习框架提供了一种形式化的方法来量化概念类的可学习性。
The state of nature has a law of nature to govern it, which obliges every one: and reason, which is that law, teaches all mankind, who will but consult it, that being all equal and independent, no one ought to harm another in his life, health, liberty, or possessions.
The night is a great mirror, but the stars are its reflections.