What is the “thesis” or “main idea”?
A thesis is the main point you are making in an essay. It is a claim that can be debated, not a statement of fact or an opinion so widely held that few would disagree with you. For example, consider the following sentences:
The first sentence is not a thesis because it simply states a fact. A paper that aimed to prove that King was African American and a minister would not be very long or very interesting. The second sentence is not a thesis because it is an opinion so widely accepted that there is no real question of debate. It is not a claim you need to prove to most readers. On the other hand, if you argue against the common wisdom as the third sentence does, you do have a thesis. The fourth sentence is also a thesis because you would need to show that the other major players in the civil rights movement were not, in fact, leaders.
In most of the essays and papers you write in college, you should explicitly state your thesis at the start of your paper. This lets the reader know where the paper is going. When you are writing for a class, it is always a good idea to let your teacher know what your point is. If the teacher has to guess at your point, he or she may not give you credit for making or fully understanding it.
In some descriptive and narrative writing assignments, you do not necessarily need to state a thesis outright. However, you should have some controlling idea that helps you decide what detail to include in your description or story and what to exclude.
In reflective and exploratory writing like journaling and some essays, you may not be required to have a thesis. In these cases, you are being asked to use writing to follow, develop and explore your ideas. The goal is not to make everything relate to your one main point, but to see where your ideas take you.
If in doubt, always ask your teacher about his or her expectations.