It's pure instinct.

这完全是本能的反应。

youdao

The thing is, my decision was made on pure instinct.

重要的是，我的决定是基于纯然的本性。

youdao

Humans part of the animal world not nearly as clever as they thought they were, reliant on brute animal instinct to find out about the world, quite incapable of knowing about things by pure reasons.

人类是动物世界的一份子，但并没有他们自认为的那么聪明，需要依赖动物本能来了解世界，而不能仅靠纯粹理性来认识事物。

youdao