In the academic world, you write to make your thinking transparent. Readers will look at the evidence you have presented and scrutinize your reasoning. If your reasoning does not bear scrutiny, readers will not accept your conclusions. Unsupported opinions are of little interest to scholars.

Scholars have engaged in intellectual reasoning for thousands of years; and they have all had to learn the rules of the game. Beginners might usefully acquaint themselves with the common errors in reasoning known as logical fallacies. In modern English, these fallacies have easy-to-remember names such as the slippery slope, and red herring. Here is an example of the fallacy known as circular argument:

George Bush is a good communicator because he speaks effectively.

This, and other examples of logical fallacies, can be found at Purdue University's online writing lab.