Language Point 48

...he had established the existence of one class of Fuchsian functions. (Para. 5)
existence: n. the fact or state of existing
This is the oldest steel bridge in existence.

这是现存的历史最悠久的钢桥。
Some people think that it is difficult to prove the existence of the unconscious mind.

有人认为难以证实潜意识的存在。