He Deductive method Is a form of reasoning that involves the formulation of hypotheses and their verification through logic.
It is a method of reasoning whose origin is attributed to Aristotle And that links premises (or previous statements from which others are inferred) with conclusions.
In it, the premises are general and the conclusions are specific. That is, universal or general laws apply to particular matters.
Deductions are characterized by having logical certainty because the conclusion is already contained within the premises.
The deductive reasoning allows to organize the premises in syllogisms that validate the conclusions. This scientific method is commonly used in research in the field of social sciences.
Another feature of this method is that if all premises considered are true, the terms are clear and the rules of deductive logic are followed, then the conclusion is necessarily true.
However, an argument can be"valid"even if one or more of its premises are false. That is why deductive arguments are evaluated in terms of their validity and solidity. That is to say, that is logical, does not necessarily mean that it is true. For it to be true or solid, its premises must be verifiably true.
This last point demands of the researcher, the rigorousness of the scientific method, to verify the veracity of the premises in case he wants to extrapolate the conclusions to other phenomena or situations. It should also be emphasized that the conclusions are usually specific.
20 examples of deductive method
In the following list there are 20 examples of hypothetical sentences that show the different"formulas"or ways of using the deductive method:
1- If Larry is ill, then he will be absent. If Larry is absent, then his class work will be lost. Larry is absent, therefore, he lost his class work.
2- If it is raining, there are clouds in the sky. There are no clouds in the sky, therefore, it is not raining.
3. Everyone who eats carrots is a field marshal. Juan eats carrots. Therefore, Juan is a field marshal.
4- The current in an electric circuit is directly proportional to the voltage and inversely proportional to the resistance (I = V / R). The resistance in a circuit is doubled, therefore, the current is cut in half.
5. Noble gases are stable. Neon is a noble gas, therefore, neon is stable.
6- The parts of the monocot flower are in the multiples of three. The flowers of the apple tree have five petals, so the apple trees are not monocotyledons.
7. The relationship of the squares of the periods of two planets is equal to the ratio of the cubes of their mean distances to the Sun. The Earth is closer to the Sun than to Mars. Therefore, the Earth orbits the Sun faster than Mars.
8- This dog always barks when someone is at the door. The dog does not bark, so there is no one at the door.
9- Sam always goes to where Ben goes and Ben went to the library. Then Sam also went to the library.
10- No one has lived more than 122 years. Then, humans die before they are 122 years old.
11- Every time I take a test in math, I fail. Today I'm taking a math test, so, I'm going to fail in my test today.
12. Jenna is in Mrs. Jones's class. Mrs. Jones's class is in the library. Jenna will be in the library.
13- All cows are mammals. Bessie is a cow. Then Bessie is a mammal.
14- All women in my family have university degrees. My aunt Joan is visiting us. So Aunt Joan has a college degree.
15- All men are equal. Ramon is a Spanish man and Xin is a Chinese man. Then Ramon and Jim are the same.
16- Spending many hours sitting does damage to health. John works in an office, sitting in front of his computer 8 hours a day. Then, John's health must be wrong.
17- Vegetables are healthy. The carrot is a vegetable. Then the carrot is healthy.
18- Reading helps to write well. Hanna reads a lot, so Hanna should write very well.
19- Mexicans eat with spicy. Nora is Mexican, so Nora eats with spicy.
20 - Mammals breastfeed their offspring. The cat suckles its kittens, therefore, the cat is a mammal.
Premises in scientific research
In scientific research, this method is also used, although it is more common the inductive, which consists in generalizing an observation from singular cases.
There are several"formulas"or ways to develop a deductive reasoning:
A) Simple : It is the most direct form of deduction, in which the conclusion logically links to premises 1 and 2.
Premise 1: All men are mortal.
Premise 2: Socrates is a man.
Conclusion: Therefore, Socrates is mortal.
B) Law of detachment : This form of deduction is also known as an affirmation of the antecedent and in it a single conditional statement is made and a hypothesis (P) is established. The conclusion (Q) follows then from the statement and from the hypothesis:
P → Q
C) Law of syllogism : Consider conditional premises and form a conclusion combining the hypothesis of a statement with the conclusion of another:
P → Q
Q → R
Therefore, P → R.
If the alarm (P) sounds when the front door is opened. The front door opens at 3 p.m. (Q), then the alarm will sound at 3 p.m. (R).
D) Law of contraposition : Supposes that, in a conditional, if the conclusion is false, then the hypothesis must be false as well.
P → Q.
~ Q.
Therefore, we can conclude ~ P.
All Chinese know about martial arts. Chu is Chinese and does not know martial arts. Therefore, not all Chinese know martial arts.
References
- Dávila Newman, Gladys; (2006). Inductive and deductive reasoning within the research process in experimental and social sciences. Laurus,. 180-205.
- Deductive Method. Retrieved from: merriam-webster.com.
- Deductive Reasoning. Retrieved from: csun.edu.
- Deductive Reasoning. Retrieved from: philosophyterms.com.
- Dudovskiy, John. Deductive Approach (Deductive Reasoning). Retrieved from: research-methodology.net.
- Examples of deductive reasoning. Recovered from: softschools.com.
- The illustrated little Larousse (1999). Dictionary encyclopedic. Sixth edition. International co-edition.