The world is full of obvious things which nobody by any chance ever observes.
It was the best of times, it was the worst of times, it was the age of wisdom, it was the age of foolishness, it was the epoch of belief, it was the epoch of incredulity, it was the season of Light, it was the season of Darkness, it was the spring of hope, it was the winter of despair, we had everything before us, we had nothing before us, we were all going direct to Heaven, we were all doing direct the other way.
逻辑学研究不仅仅是关于形式系统,更是关于人类推理的本质。