GED Science: Deductive vs. Inductive Reasoning

In science, one can develop explanations from two different perspectives.  One perspective is to start from the “bottom up.”  You would broadly make observations, describe patterns, and construct an explanation.  This is called inductive reasoning.  In inductive reasoning, you work from the specifics, and generalize from those specifics.

Inductive reasoning can be understood through the following example:

  1. Tom has had an allergic reaction to peanuts, walnuts, and stir hazelnuts.
  2. All of these food items are nuts.
  3. Therefore, Tom is probably allergic to all nuts.

Another perspective is to work from the “top down.”  You would start with an understanding of a scientific theory, and then use that understanding to make a hypothesis about a specific situation.  This is called deductive reasoning.  In deductive reasoning, you work from generalizations to the specifics.   You can think of deductive reasoning as testing existing theories and hypotheses (generalizations) by collecting experimental observations (specific examples) that put those ideas to the test.

Deductive reasoning can be understood through the following example:

  1. Every citrus fruit is a good source of vitamin C.
  2. This thing in my hand is a caracara orange (a kind of citrus fruit).
  3. Therefore, this caracara orange is a good source of Vitamin C.


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