When I was a student, it was not infrequent for me to have an idea and write an essay in one go. In the phase of editing, I could not see any faults in my essay, because I knew what I wanted to say. Much to my disappointment, when I had my essay read by somebody else, sometimes I found out that I had communicated something quite different from what I had in mind. I believe this is one of the most insidious pitfalls in essay writing. Indeed, your intentions are unfathomable (and irrelevant) to the reader: s/he will only know (and be interested in) what you have actually written. In other words, a poor word choice can fatally undermine the logic of your argument. I will now clarify this point with the aid of a simple example.
Let us suppose that you are describing an entity, which is made up of three elements standing in a certain relationship with each other: your description of this scenario must be careful and consistent; otherwise, you may find yourself in trouble. Let us also suppose that you have decided to introduce your entity as ‘A’. Later in the text, you want to provide some more details about this entity and say it is made up of the three components ‘A’, ‘B’, and ‘C’. An apparently small oversight has led you to claim, inconsistently, that ‘A’ is at the same time the whole entity and one of its three components. This already amounts to a reductio ad absurdum of your argument and you are also running the risk of going further astray. For instance, you may later term the relationship between the two components ‘A’ and ‘B’ as ‘C’. Then, you would be claiming that ‘A’ is an entity which is made up of itself and two more components, one of which (‘C’) is the relationship between ‘A’ itself and the other component (‘B’). The danger of infinite regress would then be looming large.
You may be tempted to dismiss the present post as ‘stating the obvious’ and/or dealing with a trivial issue. Though perhaps legitimate, this comment does not find support in my experience. It is true that the problem mentioned above can be resolved by rephrasing the concept, so that ‘A’ is an entity made up of three components ‘B’, ‘C’, and ‘D’, with the relationship between ‘B’ and ‘C’ being labelled ‘E’ (for the sake of completeness, let us add that the relationship between ‘C’ and ‘D’ could be labeled ‘F’ and the one between ‘B’ and ‘D’ could be termed ‘G’). However, this is the kind of issue which tends to slip under the radar. Indeed, not only can you find this kind of oversights in student essays, but also in academic books. For instance, in an otherwise well-written monograph on English phraseology, an internationally recognized linguist claimed that his analysis was “… expected to reveal very strong qualitative trends rather than statistically measurable patterns” (the emphasis is mine). This assertion is controversial because the notion of ‘trend’ is inherently quantitative, i.e. a trend is a statistically measurable pattern. Basically, the author is claiming that the analysis is expected to reveal ‘As’ rather than ‘Bs’ but he is overlooking the fact that ‘A’ and ‘B’ are extensionally identical.
Putting the above quotation into context, my guess is that the author aimed to say that the scope of his study was not carrying out a detailed statistical analysis, but rather identifying general tendencies and then proceeding to carry out a qualitative analysis. However, this is just my interpretation. In order to prevent misunderstandings in your essays, you will need to put forward sound arguments as clearly as you can. It goes without saying that, to do so, reflecting on what you want to say will be vital. However, the way you choose to say it is no less important since an unfortunate lexical choice may turn into a serious logical problem. Indeed, it seems safe to state that, in academic writing, logic and word choice must go hand in hand.