# 4 definition by ceclark

Top Definition
In logic, a fallacy is an incorrect conclusion. This may result in one of two ways.
1. If the structure of the argument is not correct at all, it is called a 'formal' fallacy. One, or both, of the first two propositions would be written incorrectly in relation to the other.
2. If the structure is correct in the first two propositions, but the conclusion is not put together properly, it is called an 'informal' fallacy.

The usual example of an argument that has no fallacy is:
Socrates is a man.
All men are mortal.
Therefore: Socrates is mortal.

Each sentence is a proposition. No propositions in an argument must be factually true to in order to create an argument with no fallacy; they must only follow the rules of logic. It is when the structure, the rules of logic, does not conform to the 256 various forms of a syllogism, it will contain a 'formal' fallacy. When only the conclusion does not follow the rules, it is an 'informal' fallacy.

Search for 'moods and figures of logic' for a full account of structure in logic.
1. It is a formal fallacy to say
Socrates is a man.
Dogs are mortal.
Therefore: Socrates is a dog. The second premise must contain either 'Socrates' or 'man' ('men), and in the right order. This is what is meant by the 'structure' of the argument.

2. It is an informal fallacy to say:
Socrates is mortal.
Dogs are mortal.
Therefore: Dogs are Socrates. The first two propositions are written correctly by the rules of logic, but the conclusion is written incorrectly.

Search for 'moods and figures of logic' for a full account of structure in logic.
by February 25, 2012

Generally, a proposition is a statement, a sentence that makes a claim such as "This water tastes bad."

There are four kinds of propositions, labeled A, E, I, and O.
An 'A' proposition claims that "All A are P."
An 'E' proposition claims that "No A are P."
An 'I' proposition claims that "Some A are P."
An 'O' proposition claims that "Some A are not P."

Propositions are used in everyday language. A simple sentence can be a proposition. A proposition is labeled for the purpose of determining its validity, its truthfulness, against other statements in logical arguments when compared to other statements in that argument.

"This water tastes bad" would be an example of an 'A' proposition, because the speaker is including all of 'this' water in his claim.
A proposition: "A restaurant is not a clean place." "All cats are felines."
E proposition: "Not one smile is on any of their faces." "No cats are canines."
I proposition: "Some candy is sickeningly sweet." "Some cats are in the species called 'lion'."
O proposition: "Some days are not good days around here." "Some cats are not in the genus called 'Panthera'."
by February 25, 2012

Belief is acceptance of a proposition, the meaning behind a declarative sentence. See example.

A belief can also be the passive acceptance of an obvious fact, such as "The car was blue" or "My father died when I was five years old". The first 'fact' is a true belief; the second sentence is a justified true belief.
I have a belief that the proposition "Red delicious apples are juicy" is true. I have a belief the proposition that "Worms grow as large as pythons" is not true.
by February 24, 2012