The pessimist believes...,

[Silverobama]

Which sentence is better and why?

a) The pessimist believes that everything has been written while the optimist believes that he can write everything.
b) Pessimists believe that everything has been written while the optimists believe that he can write everything.

 

[Rover_KE]

@Silverobama, you surely know that we need the source and author of quoted text.

 

[Silverobama]

I surely know that, Rover. I forgot to say that I wrote this sentence ( I translated it from a Chinese saying) and as you may have known, Chinese don’t have plural or singular. So I can’t decide which one to use.

 

[emsr2d2]

I surely know that, Rover. I forgot to say that I wrote this sentence ( I translated it from a Chinese saying. and As you may have known know, [the] Chinese [language] don’t doesn't have use singular/plural or singular. so I can’t decide which one to use.

Note my changes above. Although we frequently say "Surely you know ...", we don't repeat "surely" in the response. As it's a saying, you can't say "I wrote this sentence". You didn't. Someone a very long time ago came up with it. You've simply translated it.

As far as your original sentence goes, whilst I don't really understand the concept, I'd use the first sentence, using "the pessimist/the optimist" as the generic terms. I'd change "he" to "they" so it doesn't appear that you're suggesting that all optimists are male.

When you say "everything is written", are you talking about destiny/fate?

If you were to use the second sentence, you should delete "the" from before "optimists" and change "he" to "they".

 

[Silverobama]

When you say "everything is written", are you talking about destiny/fate?

Yes.

I wonder if there's a similar saying in English.

 

[emsr2d2]

Some people say that your destiny/fate is "written in the stars".

 

[tedmc]

a) The pessimist believes that everything has been written while the optimist believes that he can write everything.
b) Pessimists believe that everything has been written while the optimists believe that he can write everything.

I don't think "pessimist" and "optimist" have anything to do with being able to take charge of one's destiny as "being able to write everything" suggests.

An optimist is one who has a positive outlook in life while an pessimist is the opposite, being negative. The type you are talking about are people who are proactive, make things happen or go-getters, as distinct from those who are reactive and wait for things to happen.