Types of argument
There are different types of arguments. But based on patterns of reasoning they involve or
the strength of inferential claim arguments can be divided in to two main groups. These
are ;
1. deductive arguments
2. inductive arguments.
We differentiate them in terms of the type of support that the premises are meant to
provide for the conclusion.
1. Deductive Arguments
Deductive Arguments are arguments in which the premises are meant to provide
conclusive logical support for the conclusion. This means that if the premises are true, the
conclusion must also be true.
The structure of a deductive argument ensures that the truth of the conclusion is
guaranteed by the premises
It’s a top-down approach in which you reach a conclusion based on a premise that is
assumed to be true
Example
No student in this class will fail. Mary is a student in this class. Therefore, Mary will not fail.
The conclusion (“Mary will not fail”) is claimed to follow necessarily from the
premises (“No student in this class will fail” and “Mary is a student In this class”)
2. Inductive arguments
Inductive arguments are, by their very nature, risky arguments.
Arguments in which premises provide probable support for the conclusion. This means
that the premises suggest that the conclusion is likely, but do not guarantee it.
It involves probabilistic reasoning
Example
Ten percent of all customers in this restaurant order soda. John is a customer. Therefore, John
will not order Soda.
Since only 10% order soda, it generalizes that John is likely not among this small
group. However, because it relies on probability rather than certainty, it remains
an inductive argument.
Distinction Between Deductive and Inductive arguments
While it’s traditionally believed that inductive arguments move from particular to
general, and deductive arguments from general to particular, arguments can actually
proceed in any direction. Therefore, other methods are needed.
When interpreting an argument’s inferential claim, you need to consider three primary
factors:
1. Indicators:
- Inductive: Phrases like :-”probably,” “likely,” “possibly,” “it is plausible that” suggest an
inductive argument.
- Deductive: Phrases like ”definitely,” “necessarily,” “it is certain that” suggest a deductive
argument.
2. Strength of Inferential Link:
- Deductive: The conclusion follows with strict necessity from the premises.
- Inductive: The conclusion follows probably from the premises.
3. Forms of argumentations
It is possible for two factors within a single argument to conflict with each other, leading
to opposite interpretations
For example: “definitely , the team will win the game because they’ve won their last five
matches.”
Here, “definitely ” is used as if the conclusion is definite (deductive), but the
argument is actually inductive because it is based on the probability of future
outcomes based on past performance, which is not certain.
When these factors conflict, prioritize them as follows:
1. Arguments providing absolute support for the conclusion.
2. Arguments with a specific deductive character or form.
3. Arguments with a specific inductive character or form.
4. Arguments with inductive indicator language.
5. Arguments with deductive indicator language.
6. Arguments with premises providing only probable support.
Deductive Argument Forms
Arguments that aim to provide absolute support for their conclusions come in various
forms. Five notable types are:
Mathematical Arguments: These rely on arithmetic or geometric calculations. Since these
arguments are precise, they are deductive. However, arguments involving statistics often
generalize from sample data to populations, making them inductive.
Examples:
There are three pencils on the desk, and four more pencils are added. Therefore, there are
seven pencils on the desk. ( based on arithmetic calculations)
A circle has a radius of 5 units. Therefore, the area of the circle is 25 pi r square units
( based on geometric computation )
Definition-Based Arguments: These depend on the definitions of terms for their conclusions,
making them inherently deductive. Example: Dr. Smith is described as erudite, it follows that
he possesses extensive knowledge and learning.
Syllogism : it is a type of logical reasoning where the conclusion is gotten from two linked
premises. It has exactly 2 premise and 1 conclusion.
There are three main types of syllogisms each with its own qualities: conditional or basic
syllogisms, categorical or if/then syllogisms, and disjunctive or either/or syllogism
Categorical Syllogisms: These involve statements that begin with terms like “all,” “no,”
or “some.” They help draw necessary conclusions from given categories or classes.
Example: All humans are mortal. All mortal beings die eventually. Therefore, all humans die
eventually.
Hypothetical Syllogisms: These use conditional (“if…then”) statements in their
premises. Though sometimes viewed inductively, they are typically deductive as they
follow a logical sequence.
Example: If it rains, the ground will be wet. If the ground is wet, the flowers will grow.
Therefore, if it rains, the flowers will grow.
Both Modus Ponens and Modus Tollens are forms of hypothetical syllogisms
Example: If it rains, the ground will be wet. It is raining. Therefore, the ground is wet.( Modus
Ponens (Affirming the Antecedent))
If it rains, the ground will be wet. The ground is not wet. Therefore, it is not raining.
(Modus Tollens (Denying the Consequent)
Disjunctive Syllogism: These use “either…or…” statements in their premises to resolve
one possibility by eliminating the other, leading to a definitive conclusion
Example: Either we will go to the beach, or we will go to the mountains. We will not go to the
beach. Therefore, we will go to the mountains.
Inductive Argument Forms
Inductive arguments are designed to extend beyond the premises to reach new
conclusions. These premises often involve familiar subjects, while the conclusions
venture into less known territories. Common forms include predictions, analogies,
generalizations, arguments from authority, signs, and causal inferences.
Predictions: Arguments that use past and present knowledge to forecast future events.
Example: Observing clear skies all week, one might predict that tomorrow will also be
sunny.
Arguments from Analogy: These rely on similarities between two entities or situations to draw
a conclusion.
Example: Because Jane’s laptop model performs well, it is concluded that Mark’s
identical model will perform well too.
Generalizations: Arguments that extrapolate from a sample to the entire group.
Example: Tasting three strawberries from a basket and finding them sweet, one
concludes that all the strawberries in the basket are sweet.
Arguments from Authority: These rely on the statements of experts or witnesses.
Example: Believing a weather forecaster’s prediction of rain tomorrow because they
are an expert.
Arguments Based on Signs: These draw conclusions from signs or symbols.
Example: Seeing a sign that says “Road Closed Ahead,” one concludes that the road is
indeed closed ahead.
Causal Inferences: These arguments move from cause to effect or vice versa.
Example: Noticing a plant has wilted, one concludes it has not been watered (effect to
cause).
: It has been raining heavily for the past three hours.: Therefore, the streets
will likely be flooded.( cause to effect)
In each case, the conclusion extends beyond the premises, making inductive arguments
inherently probabilistic rather than certain
Note: Scientific arguments can be both Inductive and deductive.
Scientific laws are generalizations that hold for all times so their application to a
specific situation is always deductive.
Scientific arguments aimed at a discovery of a law of nature are inductive.
References
https://people.math.carleton.ca/~kcheung/math/books/giam-ON/html/sec-deduct.html
https://www.ditext.com/hurley/validity.html
https://study.com/academy/lesson/syllogism-definition-examples.html
https://open.library.okstate.edu/criticalthinking/chapter/__unknown__/
