主语和表语不定式为何用了不定式的完成式

To have given up one’s experience to words is to have begun marking out the limits and potential of its meaning.

这个句子里主语和表语不定式为何用了不定式的完成式？意义何在？

To have given up one’s experience to words is to have begun marking out the limits and potential of its meaning.

不定式的完成体可以作主语、宾语或表语。该句的主语和表语都是完成式（体），说明主语和表语两个动作都是根据已经发生去理解的，形成主、表对应。

【翻译】把我们的经验付诸于文字，就是开始指出其价值的局限性和潜力。

假如用不定式的一般体，仅说明是一种可能性，未经实践证明。

To climb the mountain in such weather is dangerous. 或：

It is dangerous to climb the mountain in such weather .

在这种天气爬山是危险的。

假如用动名词，则说明是习惯意义，具备常见性。

Seeing is believing. 眼见为实。