A persuasive speech depends on the power of its arguments. An argument has three parts:

A persuasive speech may stick to one type of claim, or blend several types. There are three different kinds of claims:

Claims of Fact verify the truth of something. These claims typically address questions for which competing answers exist (e.g., “Are rich people happier?”). Speculative claims of fact address questions whose answers are unknown (e.g., “Will climate change legislation help the economy?”)

Claims of Value try to show that something is right or wrong (e.g., whether the death penalty is ethical). Evidence for a claim of value is usually more subjective than the evidence offered to support a claim of fact.

Claims of Policy endorse specific courses of action (e.g., “Body cameras should be worn by all police officers to reduce the use of excessive force during arrests”). Policy claims are prescriptive, meaning they argue that the proposed action will improve the status quo.

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Evidence is material intended to convince the audience a claim is valid. Some forms of evidence include examples, narratives, testimony, facts, and statistics. External evidence, or knowledge drawn from beyond the speaker’s experience, is the most common form of evidence.

The audience’s preexisting thoughts and beliefs can also be powerful evidence for a claim. Few strategies gratify audiences more than a reaffirmation of their beliefs, especially for claims of value and policy.

Finally, when a speaker’s experience and opinions are relevant to a claim, his or her expertise can be used as evidence. However, audiences are often skeptical of claims supported solely by the speaker’s testimony. Supplementing your speaker expertise with external evidence is more likely to yield a persuasive message.

A one-sided message ignores opposing viewpoints; a two-sided message addresses opposing claims in order to weaken or refute them. As a general rule of thumb, a persuasive speech should contain a two-sided message. On the one hand, if your audience is aware of opposing viewpoints that your speech ignores, you risk losing credibility. On the other hand, it’s impossible to review and refute every single possible counterargument. The best strategy is to focus on raising and refuting only the most important counterarguments your audience is likely to be familiar with.

Reasoning is the process of drawing logical conclusions from a body of evidence.

Deductive reasoning begins with a general principle or case, is followed by an example of that case, and then concludes with a claim. If the audience accepts the general principle and the specific example, logic dictates that it must accept the conclusion.

General Case All dogs are mortal.

Specific Case Fido is a dog.

Conclusion Therefore Fido is mortal.

Inductive reasoning begins with specific cases, or minor premises, then leads to a general conclusion those cases support. However strong such conclusions appear to be, they are not always, or necessarily, true. Many inductive arguments are in fact weak. An audience must decide if a conclusion reached through inductive reasoning is a valid one based on the evidence at hand.

Specific Case 1 Papua New Guinea has recorded a rise in sea level.

Specific Case 2 Key Largo has recorded a rise in sea level.

Specific Case 3 New York City has recorded a rise in sea level.

Conclusion Sea levels are rising worldwide.

Reasoning by analogy is a form of inductive reasoning in which the speaker presents two cases and implies that what is true of one is true of the other. Analogies presume that the circumstances underlying both cases are similar, if not identical—and for this reason, such arguments can have vulnerabilities.

Causal reasoning asserts that one event or issue is the cause of another (e.g., “Widespread online bullying, combined with the large amount of time teens spend online, has led to a nationwide increase in the number of teenagers diagnosed with anxiety disorders”).

Logical fallacies are rationales for claims that may seem reasonable but are actually unsound—and usually false. Not only should you strive to avoid fallacious reasoning in your own speeches, but you should be able to identify it in others’ speeches. While many logical fallacies exist, some of the most common are defined in the following table.

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