Pros and Cons of Thesis Statements

Arguments For:

Announces and focuses purpose
The thesis is a declaration of the primary argument to both the reader and the writer. It must condense the author’s views enough to be manageable, and this often helps writers focus on exactly what they are going to argue.
Dictates scope
The structure and content of the thesis can help a writer control the size of the topic addressed in the paper. This is particularly useful when there is a page/word requirement, because it helps the author plan just how much they will be writing.
Forces an argument
Writing a thesis requires the author to take a definite position on an issue, to have an opinion, which is required for a convincing argument.
Gives the piece an easily identifiable “soul” or central theme
A thesis provides a written “center” to the paper which can be returned to and referenced in order to keep a coherent argument and stay on topic.
Easy pattern
A thesis (particularly within the structure of a 5-paragraph essay) is an easy way of organizing thoughts for a paper.

Can restrict speculation on the topic
A formal thesis will generally not work very well in a paper whose beginning purpose is to explore an issue rather than immediately take a position.
Allows for little creativity in the opening paragraph in particular
A traditional thesis can seem out of place in an opening which relies primarily on a conversational tone or humor. While these are not typical characteristics of academic, analytical writing, they are still powerful tools for making an argument, and loss of those and similar options gives the writer less to work with.
Can encourage premature/shallow arguments
While it’s not always so, writing a thesis at the beginning can tempt students into forcing or manipulating evidence in order to support it, rather than examining the evidence first and then drawing a defensible conclusion.
Thesis-focused assessment may overlook other qualities
If the thesis is “standard,” readers may automatically conclude that if a piece does not have one, it cannot have an argument, and unjustly judge its merit.