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Scientific Thinking

Reasoning can be done by induction or deduction.

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Scientific Reasoning - Advanced

License: CC BY-NC 3.0

What does it mean to reason?

"What does the data show? Did the experiment work? Is the hypothesis correct?" Reasoning is the human process used to make sense of things. Reasoning is also used to establish and verify facts. "Scientific reasoning" is no different than everyday reasoning - it is used to make sense of things related to the scientific process, such as conclusions based on the results of an experiment.

Scientific Reasoning

Any useful hypothesis will allow predictions based on reasoning. Reasoning can be broken down into two categories: deduction and induction. Most reasoning in science is done through induction.

Deductive Reasoning: Deduction

Deduction involves determining a single fact from a general statement; it is only as accurate as the statement.

For example, we know that all organisms are made of cells and need to maintain homeostasis and must reproduce to stay alive. Therefore, since humans are organisms, we can then deduce that humans are made of cells, maintain homeostasis and reproduce.

Deductions are based on valid reasoning. The reasoning in the following argument is valid, because there is no way in which the reasons 1 and 2, could be true and the conclusion, 3, be false:

  • Reason 1: All humans are mortal.
  • Reason 2: Albert Einstein is a human.
  • Conclusion: Albert Einstein (Figure below) is mortal .

Credit: Oren Jack Turner
Source: http://commons.wikimedia.org/wiki/File:Albert_Einstein_1947a.jpg
License: CC BY-NC 3.0

Albert Einstein (1879–1955) Deductive reasoning has helped us determine that Albert Einstein is a mortal being.[Figure2]

Inductive Reasoning: Induction

Induction involves determining a general statement that is very likely to be true from several facts.

For example, if we have had a test every Tuesday for the past three months, we will have a test next Tuesday (and every Tuesday after that).

Induction contrasts strongly with deduction. Even in the best, strongest cases of induction, the truth of the reason does not guarantee the truth of the conclusion. Instead, the conclusion of an inductive argument is very likely to be true, but you cannot be fully sure it is true because you are making a prediction about a fact that has yet to be proven.

A classic example of inductive reasoning comes from the philosopher David Hume:

  • Reason: The sun has risen in the east every morning up until now.
  • Conclusion: The sun will also rise in the east tomorrow.

Inductive reasoning involves reaching conclusions about unobserved things on the basis of what has already been observed. Induction is used regularly in fields such as archaeology, where inferences about the past from present are made. Inductions could also be made across outer space, as in astronomy, where conclusions about the whole universe are drawn from the limited number of observations we are able to make.


  • Any useful hypothesis will allow predictions based on reasoning.
  • Reasoning can be broken down into two categories: deduction and induction. Most reasoning in science is formed through induction.


  1. What is meant by scientific reasoning?
  2. Outline the difference between inductive and deductive reasoning.

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Use this resource to answer the questions that follow.

  1. What is the difference between inductive and deductive reasoning?
  2. What is confirmation bias?
  3. Why did investors expect Shrek 3 to be a box office hit?

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  1. [1]^ License: CC BY-NC 3.0
  2. [2]^ Credit: Oren Jack Turner; Source: http://commons.wikimedia.org/wiki/File:Albert_Einstein_1947a.jpg; License: CC BY-NC 3.0

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