《双城记》的第一卷第一章的开头“It was the best of times, it was the worst of times......”的含义？？!

“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。。。”着一段的含义 为什么这么写？

那是最美好的时代,那是最糟糕的时代;那是智慧的年头,那是愚昧的年头;那是信仰的时期,那是怀疑的时期;这是光明的季节,这是黑暗的季节;这是希望之春,这是失望的冬日;我们面前应有尽有,我们面前一无所有…

这是一个最好的时代，这是一个最坏的时代，这是一个智慧超群的年代，这是一个愚昧不前的年代，这是一个……

我当时在英语课上看到觉得特别经典，生动形象地写出了那个时代矛盾综综，双面性的特点，给我以强烈震撼……