Induction and deduction are pervasive elements in critical thinking. They are also somewhat misunderstood terms. Arguments based on experience or observation are best expressed inductively, while arguments based on laws or rules are best expressed deductively. Most arguments are mainly inductive. In fact, inductive reasoning usually comes much more naturally to us than deductive reasoning.
Inductive reasoning moves from specific details and observations (typically of nature) to the more general underlying principles or process that explains them (e.g., Newton's Law of Gravity). It is open-ended and exploratory, especially at the beginning. The premises of an inductive argument are believed to support the conclusion, but do not ensure it. Thus, the conclusion of an induction is regarded as a hypothesis. In the Inductive method, also called the scientific method, observation of nature is the authority.
In contrast,deductive reasoning typically moves from general truths to specific conclusions. It opens with an expansive explanation (statements known or believed to be true) and continues with predictions for specific observations supporting it. Deductive reasoning is narrow in nature and is concerned with testing or confirming a hypothesis. It is dependent on its premises. For example, a false premise can lead to a false result, and inconclusive premises will also yield an inconclusive conclusion. Deductive reasoning leads to a confirmation (or not) of our original theories. It guarantees the correctness of a conclusion. Logic is the authority in the deductive method.
If you can strengthen your argument or hypothesis by adding another piece of information, you are using inductive reasoning. If you cannot improve your argument by adding more evidence, you are employing deductive reasoning.
Quick Reference Guide
|Skill: Induction |
Given a specific hypothesis or observation,
one combines observation and prior knowledge to reach
a general conclusion.
|In Dr. DooRiddles, the student must generate
answers in many categories in order to find the right answer
to a riddle.|
A page from a book,
A thing you think with be;
You can put it in your table,
Or see it on a tree.
A leaf is a page in a book; lief is a syllable in the word
be-lief; a leaf is part of a table; a leaf is part of a
tree. The answer to the riddle is leaf.
Critical Thinking through Science
| Skill: Deduction |
Given a general conclusion or principle,
one determines specific consequences or applications.
To solve a Mind Benders® activity, the student is given
a body of general information with certain clues and must
then deduce the answers to specific questions.
Davis, Edwards, and Jones are an astronaut, a computer
programmer, and a skin diver. Davis is not the astronaut
or programmer. Jones is not the astronaut.
What does each person do?
Davis is a skin diver, so Jones is the programmer, and Edwards
is the astronaut.
Red Herring Mysteries