The Four Types of Evidence

Show Me The Evidence!

Formal Arguments

In written, formal arguments, the best way to build credibility with readers is to provide them with evidence. No matter what your argument might be and which side you agree with, citing strong evidence to back up your claim leaves the opposition with little to argue.

Emotional appeal is often used in oral arguments. Written arguments, however, rely on four main types of evidence. As you read further, you will see that some types are more credible than others and "hold more water" so to speak.

Statistical Evidence

The strongest type of evidence in formal writing is statistical evidence. This ranges from true, hard data presented as a percentage or number, to survey-type data. For example, statistical evidence could be:

  • 4 out of 5 experts claim that...
  • 85% of women in the United States...
  • 7 members were present during...

Statistical evidence can be proven as fact. You can actually go out and find hard information to prove your particular claim.

Testimonial Evidence

The use of celebrities as credibility evidence can be considered testimonial in nature. Many people look up to celebrities as role models in their lives. Good or bad, when a person chooses a life-path that takes them into public light, there will be many others out there who want to emulate the celebrity. These celebrity endorsements provide the second-strongest type of evidence found in formal arguments.

Testimonial evidence can also be collected from experts and authorities in a given field. Doctors, dentists, lawyers often provide expert testimonials. Their authority is not often questions. They are expected to "know their stuff."

Anecdotal Evidence

When storytelling is involved as evidence, anecdotal evidence is being used. Due to its less objective nature, anecdotal evidence is not extremely strong. When coupled with statistical or testimonial evidence, anecdotal evidence can be highly effective in determining credibility or proof.

Storytelling, although based on fact, can include quite a bit of opinion, thus making it less objective. Usually, eyewitnesses are used as providers of anecdotal evidence. They saw or experienced the phenomenon at hand are telling their version or side of the story.

Analogical Evidence

When information is scarce about something and little is known, analogical evidence is often used in a formal argument to increase credibility of the proof. If the phenomenon in question is new and little is known about it, analogical evidence that pulls in known factors about a similar phenomenon to show parallels can be an effective way to provide proof.

Due to limited knowledge about the phenomenon, in this situation, analogical evidence can be regarded as the weakest type of evidence used in formal arguments. One can only imagine and hope that the comparison-phenomenon is close enough that the results can be applied to the new phenomenon.

In the End...

All that really matters in a formal argument is whether or not the writer has credible evidence to back up what they want to say or what they are thinking. So often, we hear people say, "Prove it!" to one another.

One last little tidbit...great formal arguments not only provide credible evidence to support claims, don't forget that acknowledgment of the opposing point of view in an argument also strengthens the entire product.


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