I had a colleague once (someone I no longer work with and who will not be identified here) who told me that an ex-spouse had looked at an introductory paragraph and said, "That's not a proper introduction, try again." My colleague tried again and was told the same thing, etc... My colleague, in fact, could not write an introduction, though I did not say this in the conversation. No wonder it was an ex-spouse!
I was visiting professor 10 years ago at a university I won't name. The Graduate Students in my course were supposed to turn in a thesis, and only one out of a class of 10 could do it, write a thesis that was acceptable to me. Many articles I review for journals do not have an arguable thesis.
I learned to write introductions and theses in High School. These are basic skills that should be acquired before college, and yet colleagues and aspiring scholars have not always mastered them.
A thesis is the central claim that the article will demonstrate. You should be able to express it in a single sentence of about 30 words. It has to be broad-ranging and significant in its implications, and yet highly specific. It cannot be simply self-evident. Vagueness is fatal.
Suppose I think that the narrator of a novel is paranoid. That's an insight or the germ of one. So let's build a thesis out of this.
(1) The narrator of Over the Hills and Through the Forest is paranoid.
That's not a good thesis yet, because it looks like an isolated insight without any significance. Let's try again.
(2) Since Raimundo Pera was writing during the Patagonian dictatorship of 1934-36, he chose to use a paranoid narrator in Over the Hills and Through the Forest to reflect the general aura of paranoia experienced during this period.
Here the thesis reflects the relationship between two phenomena. That's better. Let's imagine the finished paper, though: the writer is likely to establish some background about the political situation and then go on to talk about the paranoid narrator. Boring. The writer holds to a very naive theory about how literature reflects society.