Whether you are arguing a position, proposing a solution, justifying an evaluation, or speculating about causes, you need to give reasons and support for your thesis.

Think of reasons as the main points supporting your thesis. Often they answer the question Why do you think so? For example, if you assert among friends that you value a certain movie highly, one of your friends might ask, “Why do you like it so much?” And you might answer, “Because it has challenging ideas, unusual camera work, and memorable acting.” Similarly, you might oppose restrictions on students’ use of offensive language at your college because such restrictions would make students reluctant to enter into frank debates, because offensive speech is hard to define, and because restrictions violate the free-speech clause of the First Amendment. These because phrases are your reasons. You may have one or many reasons, depending on your subject and your writing situation.

For your argument to succeed with your readers, you must not only give reasons but also support your reasons. The main kinds of support writers use are examples, statistics, authorities, anecdotes, and textual evidence. Following is a discussion and illustration of each kind of support, along with standards for judging its reliability.