Reasoning, as a way of proving arguments, comes in many different forms. Different forms of reasoning are accepted in different fields and contexts. Arguing with family members generally relies on different methods of reasoning than arguing with professors. Arguing about the aesthetics of a film generally relies on different methods of reasoning than arguing about global warming. The following are common types of reasoning:

Logic. Logic is one type of reasoning relying on the form of an argument. Logic has its roots in philosophy as a form of deductive reasoning or inductive reasoning. The most common form of logic seen in argumentation is the syllogism: an argument with a major premise, a minor premise, and a conclusion. Logical forms are either valid or not—as long as the form of the argument and the premises are true, then the conclusion must be true.  There are three regular patterns of syllogisms:


If all A is B, And if all C is A, Then all C is B.

If all cats are animals, And all tabbies are cats, Then all tabbies are animals.

If all welfare recipients are forced to work, And if all impoverished people are welfare recipients, Then all impoverished people are forced to work.


If A, then B, So if A is present, Then B is present.

If I jump, I will land, I jumped, Then I landed.

If WMD are found, war will occur WMD are found, War will occur.


Either A or B, So if A exists, Then B does not exist.

Either it is sunny or cloudy, So if it is sunny, Then it is not cloudy.

Either tax cuts help or hurt the economy, So if tax cuts help the economy, Then tax cuts do not hurt the economy

Science. Scientific reasoning is based on observation, prediction, experimentation, and repeatability. Arguers observe a phenomenon, establish a hypothesis, and perform experiments to confirm or deny their hypothesis, and repeat. There are numerous standards for testing this scientific reasoning:

  • Consistency. Scientific reasoning must be internally consistent, utilizing method that proves the argument.
  • Acceptability. Scientific reasoning must adhere to norms that will gain adherence by the audience.
  • Repeatability. Scientific reasoning must withstand refutation, alternative hypotheses, and experiments.

Visual/Aural Proof. Eye (or ear) witness forms of reasoning have long been crucial forms of providing proof (especially in court room settings.) Visual and aural forms of proof have rising importance as digital media and reproduction becomes more prominent.

Enthymemes. Seen as either truncated syllogisms or a syllogism based on reasoning from sign, cause, generalization, or analogy, enthymemes are common forms of inductive argument. An enthymeme is an argument where one of the premises is supplied by the audience--an assumption that the speaker makes when making an argument. Speakers who argue for peace assume that the audience believes peace is desirable. As you might be able to tell, most argument is enthymematic and relies on some foreknowledge of the audience's beliefs.

Storytelling. Storytelling is a common feature of all cultures and can provide context to argument as well as make arguments. Telling stories can be an effective method to gain an audience’s attention as well as make a subtle point about the content of an argument. Different standards for evaluating storytelling include:

  • Fidelity. If the story mirrors some aspect of the audience’s experience then they will likely find the story to be persuasive.
  • Character & plot development. Like any good story, both the characters and the plot must be advanced. Thin characters or plot makes the story no more than a quaint anecdote.
  • Understanding. A good story must have a good point; as fables and folk tales often do by passing on the moral of the story.

Specific instances. The types of reasoning explained above generally rely upon deductive reasoning; going from general premises that are considered true to specific conclusions (i.e., that DNA evidence is presumed to be accurate in specific instances is based on the general assumption that DNA science is sound.) Many arguments are not deductive arguments--they are inductive. These move from specific examples to more general conclusions. There are five basic categories for this type of reasoning:

Argument by Generalization. Argument by generalization assumes that a number of examples can be applied more generally. This is a form of inductive reasoning, whereby specific instances are translated into more general principles. Any time individual incidents are marshaled to prove overarching claims, argument by generalization is being used. Surveys and public opinion polls are often generalizations of what the larger group thinks based on a small, ideally representative, sample of interviewees. Arguing that the sun will rise tomorrow because it has risen for the last several years every morning is also a generalization about the future based on past events. Testing arguments by generalization can include questions like:

  • Are the examples analogous?
  • Are there enough examples?
  • Do the examples come from different times, places, and situations?
  • Are the examples specific enough?
  • Are there counterexamples?

Argument by Cause. Argument by cause attempts to establish a cause and effect relationship between two events. This is a form of reasoning that argues that the interactions of two or more incidents are not merely coincidental, but was actually related in some meaningful way. Any time an argument is advanced that explains the direct relationship between two things, argument by cause is being used. To say that beer causes drunkenness, or that drunkenness can be caused by beer is a relation of cause to effect or effect to cause. Either way, the relationship is established between two different phenomenon.

  • What is the certainty or strength of the relationship?
  • Are there alternate causes?
  • Are there alternate effects?
  • Is the relationship overly simplistic, or too complex?
  • Is the cause necessary and/or sufficient?

Argument by Sign. Argument by sign asserts that two or more things are so closely related that the presence or absence of one indicates the presence or absence of the other. This is in some ways a type of tightly linked cause and effect reasoning that has more certainty. Any time an argument generated utilizing one variable as proof of another, argument by sign is being used. Fingerprints are signs of discrete individuals, just as a footprint is an indication that someone has walked by recently. The sun rising is a sign of the morning. “Where there’s fire, there’s smoke” indicates a strong sign relationship—no fire exists without smoke. The opposite statement, “where there’s smoke, there’s fire” indicates a weak sign relationship, as there are many instances where smoke can occur without a fire (from a smoke machine, or from smoldering ashes).

  • Is the relationship strong?
  • Is the relationship automatic?
  • Is there an alternate cause?
  • Is there an accumulation of signs pointing towards agreement?
  • Are there contradictory signs present?

Argument by Analogy. Argument by analogy examines alternative examples in order to prove that what is true in one case is true in the other. This is an attempt to points out relevant parallels that could utilize experience and example as a guide. Any time an argument utilizes simile, metaphor, or comparison, argument by analogy is being used. Analogies have points of similarity as well as difference; and the relevance of each determines how persuasive the argument is. “What has worked for drug decriminalization in the Netherlands should work in the United States” is an attempt to use one circumstance to justify a similar policy in another circumstance.

  • Are there significant points of similarity or difference?
  • Are the points of similarity crucial to the comparison?
  • Are the differences irrelevant to the comparison?
  • Is the analogy strengthened by quantity, or is there just one comparison?
  • Is the analogy realistic, or is it hypothetical or fantastic?

Argument by Authority. Argument by authority relies on the testimony and reasoning of a credible source. This is an attempt to use expertise in a particular field (from parenting to religion to education) to advance a particular belief. Any time someone references authority figures to prove their argument, argument by authority is being used. “I told you to, and I’m the parent,” “The book says so,” and “Trust me, I’m a professional” are all appeals to authority. Some authorities have better reasons than others for granting adherence to their arguments.

  • Is the authority qualified to make a judgment?
  • Is the authority trustworthy and honest?
  • Is the authority experienced?