Writing an introduction should come near the end of the composition process, because it is difficult to introduce something well until you know exactly what it will be and how it will appear in its final form. When done at the right time, however, introductions are not difficult to craft effectively. One way to do so is to address your topic immediately, establish, common ground with your intended readership, point out a motivation or need for your argument and then state your principal claim. Introductions to academic essays frequently adhere to such a formula, which can be summarized as: Common Ground -> Problem Statement + Context -> Thesis Statement.
The first thing an introduction should do is establish common ground with its intended audience. “Common ground,” in this sense, refers to a set of interests or concerns that the author shares with the readers at whom the essay is aimed. It serves as a good starting point, because it gives readers an idea of what the essay will be about, what kind of knowledge the author expects them to have, and the ways in which the essay will be relevant to them.
There is no set rule for how many words or sentences it takes to establish common ground, but sometimes it takes no more than a sentence or even a phrase. For example, in one of my own essays on Leo Tolstoy, I establish common ground within one sentence: “Those who are acquainted with the life and works of Count Lev Nikolaevich Tolstoy (1828–1910) should not be surprised to ﬁnd a chapter about him in a volume on revolution.”
The sentence quoted above is the first in a chapter that appeared in a book about revolution and revolutionaries, and thus it establishes common ground by immediately addressing those topics.
If any component of an introduction is as important as the principal claim, it is the problem statement. The problem statement serves to justify the existence of the essay by pointing out the practical or conceptual problem that motivates the argument. The problem statement should be compelling and clearly articulated. It is also important to provide some context for your problem statement, and the context should proceed from the common ground you have established with your readers.
In the essay cited above, the common ground led to a summary of some biographical information about Tolstoy’s revolutionary behavior, particularly the aspects of his teachings that one might characterize as anarchism and pacifism. Thus the problem at hand is a conceptual one—how to reconcile two apparently contradictory aspects of Tolstoy’s philosophy.
Of course, not all argument-driven essays need to address conceptual problems. Practical problems can be just as compelling and can justify a written argument as much as any conceptual problem.
Practical problems are those that can be solved through pragmatic thinking and action. For example, the challenge of designing a more fuel-efficient automobile without sacrificing speed or size would qualify as a practical problem. A piece of writing arguing in favor of a certain solution to that particular problem may propose various enhancements to the engine, alterations to the shape of the car to increase aerodynamism, or use of lighter materials to construct the frame.
Conceptual problems are sometimes more difficult to articulate than practical problems, in large part because they often involve abstract ideas. In many cases, there is no conclusive solution to a conceptual problem. In such cases, the value of the conceptual problem emerges from the insight one gains from the activity of grappling with it. Conceptual problems often address ethical, metaphysical, epistemological, or other philosophical questions.
The thesis statement should come near the end of the introduction, and it should express your essay’s principal claim.
Length of an Introduction
There is no set rule for how long an introduction should be; it depends on the topic, how much common ground a writer has with the intended audience, the genre, an a number of other factors. As a rule of thumb, however, one might say it should be possible to write an introduction to an academic, argument-driven essay that constitutes 10 – 12% of the length of the entire paper.