Although in his early work Newton also used infinitesimals in his derivations without justifying them, he later developed something akin to the modern definition of limits in order to justify his work.
尽管在他早期的作品中，牛顿在他的推导中也使用无穷小的东西，但没有证明它们的合理性，他后来发展出一种类似于现代定义的限制来证明他的作品是正确的。