For example, some people agree that global warming is real and caused by human activity, but they do not believe it is a bad thing.
We should wear school uniforms because they would help reduce discipline, be cheaper than other clothing, and help create school pride. Zoos should be banned because animals need to remain in the wild, zoos cannot provide natural experiences for animals, and animals in zoos get sick and die.1. (The essay would present evidence and reasons to support that this is the moral of the novel.) 2.
A descriptive thesis makes a claim about how things your illness.) You can agree with someone about how things are even if you dont share their values.
But you cant agree on how things should be unless you share at least one value.
Therefore, In some cases a descriptive thesis may strongly imply a prescriptive argument as well (as in most of the examples above).
However, note that one can agree or disagree with the descriptive thesis regardless of how one feels about the moral question.
So my example above is not a valid thesis, because everybody knows what color the sky is.
An arguable thesis might be, for example, The sky only became blue about 1 billion years ago, when the composition of the atmosphere changed to produce the specific refraction of sunlight that makes it look blue. (I have no idea if this is true or not, by the wayits just an example.) This statement is not obvious, and it would require evidence about the nature of the atmosphere a billion years ago, and explanations of why that evidence is reliable, in order to be proved.
The explanatory thesis announces the subject to the reader; it never declares a stance which needs an argument to defend.
These explanatory theses are evident in expository essays and research essays.