Transcript Inductive vs. Deductive Reasoning

Inductive vs. Deductive
Reasoning
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?
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• Since all men are
mortal, and Socrates is
a man, Socrates is
mortal.
DEDUCTIVE
Deductive or Inductive?
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• Exploration of the
surface of Mars has
produced some
surprising facts.
Therefore exploration
of the surface of
Jupiter will produce
some surprising facts.
INDUCTIVE
Deductive or Inductive?
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• Since Chris is a good
athlete, Chris's sister
must be a good athlete
also.
INDUCTIVE
Deductive or Inductive?
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• The sun is a star; the
sun has planets;
therefore some stars
have planets.
DEDUCTIVE