贸易，贸易，还是贸易。

阅读历史，尤其是某个文明的历史，我们看到最多的大概是两个词：战争、贸易。

战争更多是一个文明衰落的原因，贸易则同时关乎文明的兴起与衰落。我们一次次看到这样的描述：

“Palenque was one of the first Maya realms to fail. ……Archaeologists have suggested that, ……Palenque’s stability may have been undermined by new maritime trade routes that shifted commerce to the coast. ”

“Meroe’s wealth and power diminished in the first millennium c.e., ……but also because control of trade had shifted to the southeast, to the kingdom of Aksum.”

“Trade was a major source of Ur’s prosperity, as rich finds from its Royal Cemetery attest. ”

促进或限制贸易的因素既有自然的（如地理位置），也有人为的（如清朝）。

以史为鉴，我们是不是能悟出点什么？