The conclusion to an essay should mirror the introduction. In the introduction, it is necessary to state what you plan to do over the course of the essay. In the conclusion, you must state what you have done.
Ideally, the conclusion should not contain new material – it should serve primarily to remind the examiner of the content of the essay, pulling his final impression of your work away from the fine detail of your argumentative paragraphs, and back toward a full appreciation of the argument as a whole.
Therefore, the conclusion should contain the same three central elements as the introduction. The reader should be reminded of your unique take on the question. The process of getting from question to answer, or at least of building the argument needed to support your proposed answer, should be summarized, and then your answer should be reiterated. It is often helpful to explicitly reference the introduction in the conclusion.
If argumentative material is worth adding at all, it should be given a paragraph to itself, before the conclusion. Bringing in a new argument within the conclusion both cramps the argument itself, robbing it of the room needed to develop fully, and making it look like an afterthought, and it gives that one argumentative point an excessively prominent place in the essay as a whole. Do you want that one point to dominate the examiner’s final impression of your argument, and of your essay?
A clean, uncluttered conclusion reflects a clean, uncluttered argument, and a well-planned, confidently executed essay.
The main difference between introduction and conclusion should lie not in the material, but in the tense used. The introduction should be written in the future tense – “I will do such-and-such, and this is how I will do it” The conclusion should be written in the perfect tense – “I have done such-and-such, and this is how I did it.” The introduction is a guide to the forthcoming paragraphs, and the conclusion is a reminder of the preceding paragraphs, and a clear statement of how they all weave together to form one cohesive argumentative strand.
This last is a key point: how do the argumentative paragraphs interact? How do they build upon each other, to create a cohesive argument? The conclusion should answer these questions.
To view part one (and find links to parts two and three) click here.