I lead a pretty mundane existence.

我过着相当平淡的生活。

《牛津词典》

I was left with puzzlement as to the existence or nonexistence of God.

我对上帝存在与否这个问题依然感到困惑。

《柯林斯英汉双解大词典》

I pulled gently at his sleeve, but he had forgotten my existence.

我轻轻地拉了拉他的袖子，但他已经忘记了我的存在。

youdao

Now I use this to cover some phrase because I'm not here talking about rejecting the existence of souls.

在此我不打算多加赘词,因为我不是来这讨论,是否该拒绝承认灵魂的存在的。

耶鲁公开课 - 死亡课程节选

I announced on the first day of class that I don't, myself, believe in the existence of a soul.

第一节课上,我就声明,本人并不相信灵魂的存在

耶鲁公开课 - 死亡课程节选

So, I infer the existence of atoms based on the fact that doing that allows me to explain things that need explaining.

所以说我推测原子的存在是基于,该假设使得我能够解释,所需解释的一些现象

耶鲁公开课 - 死亡课程节选

And therefore it was not until at the end of my schooldays, 16, 17, that I really became aware of music as a professional existence and I realised that I somehow belonged inside this absolutely strange world.

BBC: World: Analysis

Though I suppose the existence or non-existence of the u is helpful in determining whether the author is American or not.

ECONOMIST: The conflict in Georgia

Considering that both sent me to a store whose existence I later verified, I'm more inclined to blame my caffeine-deprived brain than the phones.

WSJ: Review: iPhone Google Maps lags Android version