Why should sentences not start with "there is" or "there are"? [closed]

First of all, I think your question is very interesting.

I wouldn't say sentences should not start with "there is" or "there are", because it's not a rule per se.

That said, good academic writing is about making your point as clearly and efficiently as you can. Furthermore, in academic english good sentences are short/simple sentences (contrary to other languages such as french, where complex sentences are used a lot in academic writing and seem to reflect the author's skills and depth). This is a tacit rule of the language that's a real challenge for english teachers (in France at least) because most of the time it's hard to diagnose. Personally it took me a long time to understand this, as my teachers were never able to explain what was wrong. They just did the same as yours : criticize the use of an otherwise correct phrasing that made my sentence more complex than needed.

"There is" is a neutral phrasing that (in some cases) steals importance from the real subject of the sentence. In your example, using it makes your sentence less clear and understandable. Plus it seems to show that you don't know how to use "social proof" in a sentence, specifically because you had to twist your sentence and make it more complicated in order to talk about "social proof".

Your sentence should probably have started with its natural subject, which is the way the man acted.

EDIT :

What is meant by when "it refers to something"?

"It" can refer to a previously mentionned object, but it's not always the case. In the same spirit, "there" can refer to a previously mentionned place, but it's not always the case either.

Here are some examples :

The chair is big, it takes too much space.

Here, "it" is used so that "the chair" doesn't have to be said again. But the subject of the second proposition is still the chair. What takes too much space? -> the chair. The sentence could get rid of the word "it", and become :

The chair is big, the chair takes too much space.

In the following, "it" refers to a proposition:

The chair is big, it is impossible to put anything else in the room.

Here, "it" refers to the action described later. What's impossible? -> not the chair! The sentence could get rid of the word "it", and become :

The chair is big, putting anything else in the room is impossible.

Now "it" becomes indispensable when it doesn't refer to any clear object/proposition:

It's time to go!

It doesn't refer to anything in particular. What is time? -> ???

"There" works kind of the same way. When you say :

I entered the room and there was the teacher.

Where was the teacher? -> In the room I entered.

But "there +BE" can be used without a context :

There are several ways to use this word.

Where are several ways? -> ??? anywhere, everywhere, that's not the point.

What your quote is saying is that "it" and "there" should only be used when they refer to something.

I can't completely agree on this, here's why :

In my last example, you could say "This word can be used in several ways" in order to get rid of "there are". But the sentence becomes passive, which is less simple/natural than the original one.

Clarity is not only brought via shortness of sentences, elimination of neutral words etc. Active tense is much more simple and straightforward than passive tense, and sometimes active tense should prevail over the choice of non-neutral words like "there".

The best way to know whether or not your sentence is as clear as it can be is to try different phrasings and see how they feel. Trying different ways of expressing yourself will make you learn faster, and give you a real chance to pass your message.

For instance, I have corrected this answer several times as I was writing it, finding more efficient phrasings after one or two trials. My goal is for you to understand what I am saying, and sometimes the first words I write are not the perfect ones. Success doesn't come from luck, it comes from repeated failures. Leaving your first choice of phrasing on the page is ignoring the very true fact that you have great potential but the first trial can almost always be perfected.

My only response is: indeed, your professor is not fluent in English, to have stated such baloney about English grammar!

Your sentence is grammatical but sloppy English.