Rules of Validity
-  Distributed Terms  -

2. Any Term Distributed in the Conclusion Must Be Distributed in the Premises

The rationale for this rule is based on the nature of distribution. If the predicate of the conclusion (the major term) is distributed, then the conclusion is making a statement about all of the members of that class. If that term is not distributed in the major premise, then the premise is not making a statement about all of the members of that class. So the conclusion is making a stronger claim than the premise can support--it goes beyond the information given in the premise.

The same reasoning applies to the minor term. If the minor term is distributed in the conclusion, it must be distributed in the minor premise as well.

A syllogism that violates this rule is said to have an illicit major or illicit minor, depending on which term is at fault.

Example of illicit major:
Consider the following argument:

Supporters of national health insurance want to make medical care more widely available.
None of the doctors I know supports national health insurance.

Therefore, none of the doctors I know wants to make medical care more widely available.

Here the major term (people who want to make medical care more widely available) is distributed in the conclusion but not in the major premise. The argument boils down to the claim that if you don't agree with my policies (i.e., that national health insurance is a good idea), then you don't accept my goals (making medical care more widely available). And of course that isn't true. People can share a goal but disagree about the best means of achieving it.

Example of illicit minor:

All M are P All vertebrates reproduce sexually.
All M are S All vertebrates are animals.
All S are P All animals reproduce sexually.


Comprehension

1 What is distributed in all universal categorical propositions?
a) only the subject
b) only the predicate
c) both the subject and the predicate
d) neither the subject or the predicate
2 What is distributed in all negative categorical propositions?
a) only the subject
b) only the predicate
c) both the subject and the predicate
d) neither the subject or the predicate
3 If the major term is distributed in the conclusion, must it be distributed in the premises?
a) yes
b) no
4 If the minor term is distributed in the conclusion, must it be distributed in the premises?
a) yes
b) no
5 If the major term is distributed in the major premise, then must it be distributed in the conclusion?
a) yes
b) no
6 If the minor term is distributed in the minor premise, then must it be distributed in the conclusion?
a) yes
b) no
7 Is there a term distributed in the conclusion of the following categorical syllogism that is not distributed in the premises of the argument?

All vertebrates reproduce sexually
All vertebrates are animals


All animals reproduce sexually
a) yes, the minor is distributed in the conclusion but not in the minor premise
b) yes, the major is distributed in the conclusion but not in the major premise
c) no
8 Is there a term distributed in the conclusion of the following categorical syllogism that is not distributed in the premises of the argument?

Some crimes against property are frauds
All frauds are felonies


Some felonies are crimes
a) yes, the minor is distributed in the conclusion but not in the minor premise
b) yes, the major is distributed in the conclusion but not in the major premise
c) no
9 Is there a term distributed in the conclusion of the following categorical syllogism that is not distributed in the premises of the argument?

All M are P
No S are M


No S are P
a) yes, the minor is distributed in the conclusion but not in the minor premise
b) yes, the major is distributed in the conclusion but not in the major premise
c) no
10 Is there a term distributed in the conclusion of the following categorical syllogism that is not distributed in the premises of the argument?

All M is P
Some M is not S


Some S is not P
a) yes, the minor is distributed in the conclusion but not in the minor premise
b) yes, the major is distributed in the conclusion but not in the major premise
c) no
11 Is there a term distributed in the conclusion of the following categorical syllogism that is not distributed in the premises of the argument?

All P are M
All M are S


All S are P
a) yes, the minor is distributed in the conclusion but not in the minor premise
b) yes, the major is distributed in the conclusion but not in the major premise
c) no
12 Is there a term distributed in the conclusion of the following categorical syllogism that is not distributed in the premises of the argument?

All M are P
No S are M


No S are P
a) yes, the minor is distributed in the conclusion but not in the minor premise
b) yes, the major is distributed in the conclusion but not in the major premise
c) no

The Middle Term | Distributed Terms |
Two Negative Premises | Negative Premises and Conclusions

Rules of Validity

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