Article of the Week

Run-On Sentences

Run-on sentences occur when writers try to combine more than one idea into a single sentence. They cause confusion because readers are not sure when one idea ends and the next one begins. Read our entry and test your knowledge with our quiz!

Using Logic

Argumentative papers make claims, and then supply evidence to support those claims. When planning your paper, it is helpful to break down your evidence into its logical elements. Then you can test the elements to determine if they are logical: both valid and true.

  1. Inductive Reasoning
  2. Deductive Reasoning

Inductive Reasoning

There are two main styles of logic: inductive and deductive reasoning. Inductive reasoning, also called induction, begins with a specific premise, and then moves to a general conclusion:

Premise 1: the Sun rose today.

Premise 2: the Sun also rose yesterday.

Conclusion: the Sun will rise every day.

This piece of induction begins with a specific piece of information, in this case an observation: the Sun has risen. We follow this with a second observation: the same behavior occurred the previous day. From this specific piece of information, we reach a general conclusion that the Sun will continue to rise each day. Because we have observed repeated behavior, the conclusion is likely. But it is not 100% valid.


Inductive reasoning can sometimes fail, as in the example of the black swan.

Premise: All of the swans I have seen are white.

Conclusion: All swans are white.

Black swans are rare, which is why the person in this example hasn’t seen one. But they do exist, so the conclusion does not follow from the premise.


Deductive Reasoning

Because inductive reasoning is not totally valid, writers often prefer deductive reasoning. Deduction moves from general premises to a specific conclusion.

Premise 1: Smoking causes lung cancer.

Premise 2: Jared smokes.

Conclusion: Jared is at risk for lung cancer.

Here, the first premise is a general statement, but it leads to a more specific conclusion.


Whether using inductive or deductive reasoning, make sure that your argument is both valid and true. In a valid argument, the conclusion follows from the premises. A true argument will have premises that can be confirmed. The above example is valid, because if Jared smokes, and smoking causes lung cancer, then Jared is at risk for lung cancer. It is true only if we can confirm the premises—that smoking causes lung cancer, and that Jared smokes. This statement would not necessarily be true if the premise that Jared smokes is incorrect. For examples of untrue and invalid arguments, see our section on Logical Fallacies.


When outlining your paper, it can be helpful to organize the paper and your paragraphs by the premise/conclusion model. Your thesis statement is a way of writing the main premise and conclusion:

Smoking should be banned in public places (conclusion) because secondhand smoke can cause nonsmokers to develop lung cancer (premise).

Each paragraph will prove a part of your argument, so it will need its own premises and conclusion. The evidence you supply proves that your premises are true, while logic will prove that your conclusion is true.