# Inductive and Deductive Reasoning

#### Deduction

Deduction: In the process of deduction, you begin with some
statements, called 'premises', that are assumed to be true, you then
determine what else would have to be true if the premises are true. For
example, you can begin by assuming that God exists, and is good, and
then determine what would logically follow from such an assumption. You
can begin by assuming that if you think, then you must exist, and work
from there. In mathematics, you can also start will a premise and begin
to prove other equations or other premises. With deduction you can
provide absolute proof of your conclusions, given that your premises
are correct. The premises themselves, however, remain unproven and
unprovable, they must be accepted on face value, or by faith, or for
the purpose of exploration.
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Examples of deductive logic:
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All men are mortal. Joe is a man. Therefore Joe is mortal. If the
first two statements are true, then the conclusion must be
true.
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Bachelor's are unmarried men. Bill is unmarried. Therefore, Bill is
a bachelor.
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To get a Bachelor's degree at Utah Sate University, a student must have 120 credits. Sally has more than 130 credits. Therefore, Sally has a bachelor's degree.

#### Induction

Induction: In the process of induction, you begin with some data,
and then determine what general conclusion(s) can logically be derived
from those data. In other words, you determine what theory or theories
could explain the data. For example, you note that the probability of
becoming schizophrenic is greatly increased if at least one parent is
schizophrenic, and from that you conclude that schizophrenia may be
inherited. That is certainly a reasonable hypothesis given the data.
However, induction does not prove that the theory is correct. There are
often alternative theories that are also supported by the data. For
example, the behavior of the schizophrenic parent may cause the child
to be schizophrenic, not the genes. What is important in induction is
that the theory does indeed offer a logical explanation of the data. To
conclude that the parents have no effect on the schizophrenia of the
children is not supportable given the data, and would not be a logical
conclusion.
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Examples of inductive logic:
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This cat is black. That cat is black A third cat is black. Therefore
all cats are are black.
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This marble from the bag is black. That marble from the bag is
black. A third marble from the bag is black. Therefore all the marbles
in the bag black.
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Two-thirds of my latino neighbors are illegal immigrants. Therefore, two-thirds of latino immigrants come illegally.

Most universities and colleges in Utah ban alcohol from campus. That most universities and colleges in the U.S. ban alcohol from campus.

Deduction and induction by themselves are inadequate to make a
compelling argument. While deduction gives absolute proof, it never
makes contact with the real world, there is no place for observation or
experimentation, no way to test the validity of the premises. And,
while induction is driven by observation, it never approaches actual
proof of a theory. Therefore an effective paper will include both types
of logic.
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