A paper's thesis states clearly what the paper is going to argue, or prove. It identifies a question, or a set of related questions, and offers a brief preliminary answer, to be developed in detail in the main body of the paper. The thesis is usually embedded in a paper's first paragraph or, in any case, is located somewhere up front, close to the paper's beginning. It holds your paper to a mission: this is what the paper will prove; these are the questions the paper will answer.
Note that a thesis is not necessarily the same thing as an introduction. An introduction (the opening of a paper) sets the scene: it establishes the paper's basic topic, its timeframe, main players, etc. An introduction does not, however, establish any claim nor identify any questions to be answered. These - the components of your thesis - usually follow only after the paper's introduction has set the scene. Often a research papers's first paragraph begins with the introductory statements, which then merge with, or into the thesis.
Because a thesis is usually placed close to the beginning of a paper, students assume that it is also among the first parts of a paper they must write. This is not necessarily the case. Yes, you should begin the process of writing with what we'll call a working thesis, i.e., an assumption as to which questions you wish to engage, and what the answers to those questions will be. However, as your writing of the actual paper proceeds, you will often find that your focus shifts: new questions arise as you go along, old questions seem less relevant, and the answers you thought you were going to provide suddenly no longer suffice. This is why you should think of your thesis as an organic, evolving set of questions and answers, rather than an inflexible mission statement whose aims and claims your paper must serve, no matter what.
We have in fact found that the best theses are sometimes written after the main body of the paper has taken shape. After all, it is only upon having completed the main bulk of their paper that writers truly know what, exactly, they have proven. By insisting on finalizing their thesis before they've written the rest of the paper, however, many student writers end up with a thesis that bears little relation to the paper itself, and conclude with the kind of statements they should have placed in the thesis.
Our advice: do not waste a large amount of time on your thesis up front. Develop a working thesis: a preliminary set of questions or claims you think you will answer, or prove. Instead of spending more time on the thesis than that, move on to the main body of your paper. Develop your examples, your evidence, your claims. Having done so, and having formulated a conclusion, review the main body of your paper, then return to the beginning: now is the time to finalize your thesis. How well does your working thesis set up the material that follows? Are your initial claims/questions still relevant? If not, tweak them so that they more effectively set up that which follows in the main body of the paper. And what about that conclusion? Have you placed statements in there which might better serve your thesis up front? If so, cut and paste them into the thesis, re-wording them slightly if necessary. (This of course will also require that you edit your conclusion a little, on which, see Formulating a Conclusion.)
For an example of how a thesis develops over time, click here
In our section on research papers, we developed a thesis for our topic of "The Austrian Catholic Church and the Anschluss." Initially, we were not entirely sure what our main questions on this topic were, nor their answers. They had something to do with the level of responsibility the Austrian church bore for its collaboration with the Nazis, that we knew, but we were unsure whether that level of responsibility was high, moderate, or perhaps nonexistent.
Our working thesis - following the recent turn in the historiography on the issue (on which, click here) - was that, whereas historians had traditionally considered the Catholic Church to have been guilty of collaboration with the Nazis, the fact is (we had read) that behind the scenes, popes and cardinals had done their best to resist the Nazis even while publicly paying them lip service. This working thesis was challenged, however, by the fact that we did find evidence of lip service, even outright collaboration among the leadership of the Austrian Catholic Church, but little evidence of any resistance. On the other hand, our research unearthed many examples of resistance at the grassroots level of the church: among priests, nuns, and other lower-ranking clergy.
So we revised our working thesis to reflect what we now recognized as the more fundamental issue at stake: that although the lower-ranking clergy had shown considerable courage and heroism in standing up to the Nazis, the leadership had, generally speaking, failed to do so. This, ultimately became the thesis embedded within our introductory paragraph, reproduced in full below. Note that the opening statements are introductory: they set the scene by introducing the topic, the timeframe, and some of the main players. Only towards the end of the paragraph do we present our thesis itself (underlined), in which we establish what it is we're going to prove:
Wedged between Nazi Germany and fascist Italy, Austria had maintained a fragile independence during the early 1930s under successive right-wing pro-Catholic Christian Socialist governments led by Engelbert Dollfuss (1932 - 1934) and Kurt von Schuschnigg (1934 - 1938). Following Nazi Germany's March 1938 annexation of Austria, however, the once socially dominant Catholic Church of Austria chose to collaborate with the Nazi regime - a decision it would soon regret. Early Catholic support following the Anschluss greatly contributed to the Nazis' acceptance among the general Austrian population. Yet once having consolidated their rule, the Nazis turned on the church and stripped it of all power. While there was significant resistance among Catholics at the grassroots level, Austria's Catholic leadership repeatedly failed to take a stand against the regime. Thus the story of Austrian Catholics under Nazi rule from 1938 - 1945, though marked by considerable heroism among the lower-ranking clergy and laypeople, is ultimately one of failed leadership. By reviewing the Anschluss and the years that followed, and by contrasting local acts of Catholic resistance with repeated acts of official collaboration at the highest level, this paper will show how Austria's Catholic Church, as an institution, lost not only its dominant social position during the years 1938 - 1945, but also much of its claim to moral authority.