解答：
这里的such是代词，该句是个倒装句，意思是“人性就是如此”。
2. 详解such:
such 可以作形容词（这样的、 如此的）、代词（这样的事物或人）。例如：
We could not believe such a thing. 我们简直不相信竟然有这种事情。
I think most of us don't want to read what's in the newspaper anyway in such detail. 我想我们大多数人无论如何都不想如此仔细地去读报纸。
Such is Mary. 玛丽就是这样（的人）。
Such is my impression of London. 我对伦敦的印象就是这些。
3. such句型及短语：
1) such+a/an（+形容词）+ 单数的可数名词:
He is such a (lazy) man. 他就是这样(这么懒惰的）一个人。
2) such （+形容词）+复数名词或者不可数名词：
People all like such (beautiful) houses.人们都喜欢这样（漂亮）的房子。
3) such+名词 +that引导的结果状语从句：
She is such a clever girl that we all like her. 她是一个聪明的姑娘，我们大家都喜欢她。
4) such +名词 + as引导的定语从句 =名词+ such as / which, that , who等引导的定语从句：
I can answer such a question as you raised just now = I can answer the question such as / (which / that ) you raised just now. 我能回答你刚才提出的问题。
Can I see such a man as was mentioned just now = Can I see the man such as / who was mentioned just now?我能见见刚才提到的那个人吗？
5) such as... = like ... 例如......：
I like many subjects, such as / like English, maths, physics and so on. 我喜欢多种学科，例如英语、数学、物理等等。
6) such (+名词）as to do... 如此（......)以至于......：
This is such a difficult math problem as to puzzle all the students. 这道数学难题难住了所有的学生。
The illness is not such as to cause death. 这种病还不至于导致死亡。
7) as such... 像这样的人或事物, 以这种名义、身份或资格, 像这样的情况, 照这样, 就这点而论,本身:
I cannot accept your gift as such. 你这样的礼物我不能接受。
As such, it is not completely convincing. 仅此还不足以令人信服。
Money as such does not bring happiness. 钱本身并不给人带来快乐。
Soldiers as such, deserve respect. 这样的士兵是值得人尊敬的。
No one writer inspired me as such. 没有一个作家如此地打动了我。
8) such +as it is 尽管不怎么样, 虽然不怎么好, 尽管没什么价值或重要性, 尽管不一定正确：
Of course you can stay for supper, such as it is. 当然, 你可以留下来吃晚饭, 尽管饭菜不好。