Inductive vs. DeductiveReasoning

Descriptions and examples

Types of Reasoning• Deductive

reasoning goes from general to specific

• Inductive reasoning goes from specific to general

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Deductive Reasoning

• Deductive reasoning starts with a premise, which we accept to be true. Then, from that rule, we make a conclusion about something specific.

• Example:• All turtles have shells• The animal I have captured is a turtle• I conclude that the animal in my bag

has a shell

Deductive Reasoning

• A conclusion reached with deductive reasoning is logically sound, and airtight, assuming the premise is true.

• If a penny is a flat disc, copper in color and has a profile of Honest Abe on it, then I can be sure the penny in my pocket has those qualities.

Deductive Reasoning

• The strength of deductive reasoning is that conclusions derived with it are fully certain.

• The weakness, which was illustrated in the most recent example, is that no new information is added.

• The fact that the penny in my pocket is a copper disc with Lincoln on it was clear from the initial data, so the conclusion hasn't added any new information.

Inductive Reasoning

• Inductive reasoning is making a conclusion based on a set of experiences or data. If I observe that something is true many times, concluding that it will be true in all instances is a use of inductive reasoning.

• Example:• All sheep that I've seen are white• All sheep must be white

Inductive Reasoning

• The strength of inductive reasoning is that new information came be stated.

• The weakness is that the new information cannot be proven.

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Deductive Reasoning

• All dogs are mammals and mammals have kidneys.

• Therefore your dog has kidneys.

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Deductive Reasoning

• All squares are rectangles, and all rectangles have four sides.

• All squares have four sides.

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Deductive Reasoning

• All chemists are smart if chemists are scientists and all scientists are smart.

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Inductive Reasoning

• All swans we have seen have been white; therefore all swans are white.

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Inductive Reasoning

• All swans we have seen have been white; therefore the next swan we see will be white.

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Inductive Reasoning

• All known planets travel about the sun in ellipitical orbits; therefore all planets travel about the sun in ellipitical orbits.

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Deductive or Inductive?

• Since all men are mortal, and Socrates is a man, Socrates is mortal. QuickTime™ and a

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DEDUCTIVE

Deductive or Inductive?

• Exploration of the surface of Mars has produced some surprising facts. Therefore exploration of the surface of Jupiter will produce some surprising facts.

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INDUCTIVE

Deductive or Inductive?

• Since Chris is a good athlete, Chris's sister must be a good athlete also.QuickTime™ and a

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INDUCTIVE

Deductive or Inductive?

• The sun is a star; the sun has planets; therefore some stars have planets. QuickTime™ and a

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DEDUCTIVE