An argument is a statement that expresses an idea. As such, it seeks to confirm, refute or explain the statement. In logic, every argument has two parts: the premises (propositions that affirm or deny something) and the conclusion.
There are several types of arguments. In the area of propositional logic and predicates, we find deductive arguments and inductive arguments. Both are ways of reasoning that reach conclusions in different ways.
- deductive arguments. They draw a conclusion from the premises. Due to its logical form, for the argument to be valid, if the premises are true, its conclusion must also be true. Thus, deductive arguments have a logical basis, their conclusion is contained in the information of the premises.
For example:
Premise 1: Dogs bark.
Premise 2: Jaco is a dog.
Conclusion: Jaco barks. - inductive arguments. They draw a conclusion from certain observations or particular experiences. Inductive arguments start from an observation and then generalize. They draw a conclusion based on probabilities and intuition.
For example:
Premise 1: Maria ate chocolate and her belly hurts.
Premise 2: Sandra ate chocolate and her tummy hurts.
Bottom line: If you eat chocolate, your tummy will hurt.
Characteristics of deductive arguments
- They are explanatory, they do not arrive at new information but they verify the existing one since the information of the conclusion is included in the premises.
- Their conclusions may be valid or invalid.
- They are used in logic and mathematics.
Characteristics of inductive arguments
- They are augmentative, they can generate new content because the conclusion has more information than exists in the premises.
- They have a certain degree of validity: they are likely or unlikely. They do not have a logical basis, the validity of the premises does not guarantee the conclusion.
- They are useful in science and serve to formulate new hypotheses through empirical data.
Examples of Deductive Arguments
- Dairy provides calcium.
Yogurt is dairy.
Yogurt provides calcium. - October 12 is a holiday.
Today is October 12.
Today is a holiday. - Plants need water to live.
Roses are plants.
Loses need water to live. - The teachers of the institution wear an apron.
Amalia is a teacher at the institution.
Amalia wears an apron. - José must pass the exam to graduate as a doctor.
José did not pass the exam.
José did not graduate as a doctor. - The minimum age to enroll in the school is five years.
Juana is less than five years old.
Juana is not of the minimum age to enroll in school. - The green peaches have not ripened.
This peach is green.
This peach has not ripened. - Lightning bolts light up the sky.
There is lightning.
The sky lights up. - Sofia’s daughters are blonde.
Carmela is Sofia’s daughter.
Carmel is blonde. - My aunt’s son is my cousin.
Gastón is my aunt’s son.
Gaston is my cousin.
Examples of inductive arguments
- It’s hot in my apartment.
It’s hot in my neighbor’s apartment.
It’s hot in the whole building I live in. - Felipe is sweet and hardworking.
Fernanda is a sweet and hardworking person.
People whose name starts with F are sweet and hardworking. - A young woman on a bicycle went through a red light.
A young man on a bicycle went through a red light.
All young people on bicycles go through red lights. - Catalina’s suitcase is black.
Lucía’s suitcase is black.
Pedro’s suitcase is black.
The suitcases are usually black. - Deputy Santiago Rojas wears a suit in each session of Congress.
Deputy Roberto Garcian wears a suit in every session of Congress.
All deputies wear suits in sessions of Congress. - Jorge plays basketball and is tall.
Bruno plays basketball and is tall.
Simón plays basketball and is tall.
Damien plays basketball and is tall.
Everyone who plays basketball is tall. - The plants on my balcony are green.
The plants on my next-door neighbor’s balcony are green.
The plants on my neighbor’s balcony across the street are green.
All plants are green. - Yesterday there was a strike in the Madrid metro.
Today there is a strike in the Madrid metro.
The Madrid metro usually makes many stoppages. - Carlos is Mexican and is very sociable.
Asunción is Mexican and is very sociable.
Mexicans are sociable. - The supermarket in my neighborhood has very high prices.
The pharmacy in my neighborhood has very high prices.
The shops in my neighborhood are very expensive.
References
- Gamut, LTF, & Durán, C. (2002). Introduction to logic. Buenos Aires, Argentina: Eudeba.
Follow with: