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Fallacies of Invalid Form

 

 

Whenever a logical fallacy is committed, the fallacy has its roots in Agrippa's trilemma which is simply the fact that the foundation of all human thought (without Divine revelation) is one of three unhappy possibilities. These three possibilities are infinite regression, circular reasoning, or bare assertions without any evidence.

 

Fallacies of Invalid Form (Formal Fallacies: Getting mixed up in thinking)

  • Formally Correct Fallacy / According to the Rules Fallacy (type of): occurs when it is thought that logic is sound because it is valid. Sound logic has true premises and a true conclusion. The formally correct fallacy results from two errors in thinking. One is an ambiguity of context regarding the kind of logic. The other is an ambiguity regarding how truth can be known. Some teachers of logic give the impression that a formally valid argument, that is, a set of statements that follow a valid form, is necessarily true. Part of this problem may stem from symbolic logic, e.g. Boolean algebra, since in these, the word, "true," is simply a "logical state."  This definition for the word, “true,” is so distant from the normal usage of the word that it is a homonym that is both a homograph and a homophone. It sounds the same and is spelled the same, but it is a different word with a different meaning altogether.
  • Logical Fallacy of Affirming the Consequent / Fallacy of the Undistributed Middle Term / Converse Error Fallacy / Fallacy of the Converse: occurs in a categorical syllogism, when the middle term is not distributed. According to the rules of logic, a term is "distributed" when a sentence says something about everything the term designates. A syllogism is invalid if both middle terms are undistributed. INVALID FORM "If P then S. S. Therefore, P." EXAMPLE "If big bang happened, then we would expect to find cosmic microwave background radiation. We do find cosmic microwave background radiation. Therefore, the big bang happened." There are many examples of this fallacy being used to "prove" things that are not true.
  • Logical Fallacy of Commutation of Conditionals / Fallacy of the Consequent / Converting a Conditional / Switching the Antecedent and the Consequent: occurs when it is reasoned that since one thing being true means that a second thing is true, this means that when the second thing is true, that means that the first thing is also true. That doesn't always work.  INVALID FORM  "if P is true, then S is true; therefore, if S is true, P is true."
  • Logical Fallacy of Affirming a Disjunct / Fallacy of the Alternative Disjunct / False Exclusionary Disjunct / Affirming One Disjunct / Logical Fallacy of the Alternative Syllogism / Asserting an Alternative / Improper Disjunctive Syllogism / Fallacy of the Disjunctive Syllogism / Fallacy of Excluson: occurs when it is assumed that if one of two options is true then the other must be false. This only applies when the or is not an exclusive or. INVALID FORM "A or B. A. Therefore, not B."
  • Logical Fallacy of Denying the Antecedent: occurs when the inverse is inferred from the original statement. INVALID FORM "If A, then B.  Not A. Therefore, not B."
  • Illicit Process: occurs when a term which is distributed in the conclusion is undistributed in the premise of any categorical syllogism.
  • Logical Fallacy of Illicit Major / Illicit Process of the Major: occurs when a premise is stated referring to only part of the class, but the conclusion refers to the whole class. Another way to state this is that a major term which is distributed in the conclusion is undistributed in the major premise of any categorical syllogism. INVALID FORM "All A are B. No C are A. Therefore, no C are B."
  • Logical Fallacy of Illicit Minor / Illicit Process of the Minor: occurs when the minor term of any form of categorical syllogism is distributed in the conclusion, but not in the minor premise. INVALID FORM "All A are B. All A are C. Therefore, all C are B." INVALID FORM “All A are B. All A are C. Therefore, all B are C.”
  • Logical Fallacy of Invalid form using "Some": two ways that people get their logic off base using the word, "some." INVALID FORM "Some A are B. C is an A. Therefore, C is B." INVALID FORM "Some A are B. Some B are C. Therefore, some A are C."
  • Unwarranted Contrast / Some Are-Some Are Not: occurs when it is assumed that because some of one thing have a certain characteristic, then some of that thing must not have that characteristic or vice versa. INVALID FORM “Some A are B. Therefore, Some A are not B.” “Some A are not B. Therefore, Some A are B.”
  • Logical Fallacy of Denying a Conjunct: occurs when someone makes a statement that two things cannot both be true and then concludes that because one of the things is not true the other has to be true. INVALID FORM "Not both S and P. Not S."
  • Logical Fallacy of Negative Premise / Illicit Negative / Drawing a Positive Conclusion from Negative Premises / Drawing an Affirmative Conclusion from Negative Premises Fallacy: occurs when the conclusion of a standard form categorical syllogism is affirmative and one or more of the premises are negative. To be valid form, a categorical syllogism that has a negative premise must have a negative conclusion. INVALID FORM "A is not a subset of B." "B is (is not) a subset of C." "Therefore, A is a subset of C."
  • Logical Fallacy of Drawing a Negative Conclusion from Affirmative Premises  / Illicit Affirmative: occurs when a negative conclusion is drawn when both premises of a categorical syllogism are not also negative, that is, one or both premises are positive. INVALID FORM "All A is B. All B is C. Therefore, some C is not A."
  • Logical Fallacy of Existential Instantiation / Existential Fallacy: occurs when a conclusion that is known to be in existence is drawn from premises that cannot be shown to be part of reality. This is a little complex to understand, and the fact that some textbooks get it wrong doesn’t help. This is talking about something called categorical form of a categorical proposition. A categorical proposition is made up of a subject and a predicate that are joined by a verb: "All S are P, No S are P, Some S are P, Some S are not P." They don’t include a verb that indicates existence. If you want to talk about existence, you must put it into the predicate. For instance, “All real things are in existence. ” INVALID FORM "All A are B. All C (not able to establish the existence of any C) are B. Therefore, some C are A." (This is only an existential fallacy if the word, "some," is understood to mean at least one. If we have not established that even one C exists, then we cannot conclude that some C exist.) EXAMPLE "All fossils are the remains of dead things that once lived. All transitional forms are fossils. (No transitional forms have ever been confirmed to exist.) Therefore, some transitional forms are the remains of dead things that once lived." This conclusion implies that there is at least one instance of a transitional form, but, while at any point in time, there are several claimed instances, over time, these claimed instances are abandoned as mistakes and new ones are claimed.
  • Fallacy of Exclusive Premises: occurs when a syllogism has two negative premises. Only one premise can be negative if the conclusion is negative. With two negative premises, you cannot support a negative conclusion or a positive conclusion. If both of the premises are positive, you cannot support a negative concluson. If the conclusion is positive, both premises must be positive. If the conclusion is negative, one of the premises must be negative and the other premise must be positive. INVALID FORM  "No A are B. Some B are not C. Therefore, some C are not A." INVALID FORM  "No A are B. No B are C. Therefore, no C are A." EXAMPLE "No Christians are Atheists. Some Atheist are not Evolutionists. Therefore, some Evolutionists are not Christians." The conclusion may be true, but the logic is not sound.
  • Logical Fallacy of Four Terms: occurs when a fourth term is included in a syllogism.
  • Logical Fallacy of Necessity / Felacia Necassitas: occurs when the conclusion of a syllogism indicates necessity, but this same necessity is not stated in both premises. INVALID FORM "A is necessarily B. C is B. Therefore, C is necessarily B."
  • Logical Fallacy of False Conversion / Illicit Conversion: occurs when the terms of a premise are switched in the conclusion when the premise uses the word all, some or no. INVALID FORM "All A are B. Therefore, all B are A." INVALID FORM "No A are B. Therefore, no B are A."INVALID FORM "Some A are B. Therefore, some B are A."
  • Logical Fallacy of Illicit Contraposition occurs when the subject and predicate terms of a categorical proposition are swapped and negated (adding not or no). INVALID FORM "No A are B. Therefore, no non-B are non-A."INVALID FORM "Some A are B. Therefore, some non-B are non-A."
  • Logical Fallacy of Negating Antecedent and Consequent / Improper Transposition: occurs when the antecedent and consequent are transposed in the conclusion and the negation is reversed in propositional logic. INVALID FORM "If A then B. Therefore, if not-A then not-B."INVALID FORM "If not-A then not-B. Therefore, if A then B."
  • Illicit Substitution of Identicals / Hooded Man Fallacy / Masked Man Fallacy / Intentional Fallacy / Leibniz' Law Fallacy: occurs when the two ways of knowing: knowing of a thing and the knowing of the thing under all its various names or descriptions are mixed in a logical argument. EXAMPLE "My biology professor says that evolution is fact. My philosophy professor says that, if evolution is fact, then God doesn't necessarily exist. Therefore, God does not necessarily exist." The most that could be concluded would be to say, "Therefore, I think that God does not necessarily exist." Two opinions cannot produce a fact.
  • Confusing "if" with "if and only if": occurs when, during the course of reasoning, an "if" changes its meaning to "if and only if." A conditional statement can be made to claim that one thing is true/false if a second thing is true/false. The form would be, “If A, then B.” This is different from saying that one thing is true/false if, and only if, a second thing is true/false. The form would be, “If A, then B, but if not A, then not B." which is equivalent to "If, and only if, 
    A, then B." INVALID FORM “If A, then B. Not A. Therefore, not B.” The problem is that we don’t know that B is not true from this logic. EXAMPLE “If I heard God leading me, and He would give me anything I asked for when I pray, then I could know that God exists. I have never heard God’s Voice, nor do I get what I pray for. Therefore, God doesn’t exist.” Of course, the real fallacy here is the false statement that this person has never heard God’s Voice. The difference is between hearing and ignoring or hearing and acknowledging/obeying. Getting back to this particular fallacy, the statement should have been, “If and only if . . .”
  • Logical Fallacy of Invalid form using "Or" / Confusing "Inclusive Or" with "Exclusive Or": occurs when an inclusive or is confused with an exclusive or. Another way to state this is that it occurs when an "or" changes its meaning to "exclusive or" during the process of reasoning. INVALID FORM "A or B. A. Therefore, not B." EXAMPLE Bill Nye, arguing against Creation Science: “There is a large variety of skulls shapes or God created Adam and Eve and everyone descended from them. There is a large variety of skull shapes. Therefore, God didn’t create Adam and Eve and everyone did not descend from them.” Bill didn’t state this logic plainly as this example paraphrases it. He used innuendo. If Bill could have proven an exclusive or for this statement, then he could have avoided this fallacy.
  • Confusion of Necessary with a Sufficient Condition: occurs when something that is necessary for an event or condition is sufficient to assure that the event or condition will occur. INVALID FORM "if A is true, then B is true; B is true, therefore A is true." EXAMPLE “They said that if I pray to Jesus, He will make Himself real to me. I knew that was false because He doesn’t exist, so I prayed just to prove it. He didn’t make Himself real to me just as I thought. And I even crossed myself and held some Rosary beads! See. Jesus doesn't exist. This proves it.”
  • Galileo Wannabe Fallacy / Galileo Argument (Formal): occurs when an appeal to pity fallacy is committed while making a comparison to what Galileo went through. Of course, this is very rarely done, but it perhaps has happened at least once. More often, this fallacy is used for fallacy abuse. The Galileo Wannabe Fallacy / Galileo Argument can take one of two different forms. One is to state it as a fake formal fallacy and the other is to state it as an informal fallacy of appeal to pity. EXAMPLE "Galileo was ignored, suppressed, and censored and he was right. I am ignored, suppressed, and censored, therefore, I am right." Of course, if this statement were ever made, it would be a fallacy. The statement was never made. It is a straw man argument. The fact is that anyone who doesn't bow to the Big-Bang-Billions-of-Years-No-Flood-Molecules-to-Man story will be ignored, suppressed, and censored. That proves that something is dreadfully wrong with the system. It proves that the scientific system is still in the same status as it was when Galileo was ignored, suppressed, and censored. Human nature has not changed. FALLACY ABUSE Sandy: "If the Big-Bang-Billions-of-Years-No-Flood-Molecules-to-Man story isn't the only possible answer to the history of the Universe, then why are there no articles defaming it in the Secular Humanist scientific journals." Rocky: "Because, just as in Galileo's day, the ruling elite among the scientists protect their sacred cow theories." Sandy: "So, your reasoning is: Galileo was ignored, suppressed, and censored, and he was right. You are ignored, suppressed, and censored. Therefore, you are right. That is faulty logic." Rocky: "That is not my reasoning. That is your straw man argument." In this case, the Galileo Argument or the Galileo Wannabe Fallacy is being used to commit fallacy abuse. Here, it is merely a defense for an appeal to tradition fallacy. One website titled their article: "The Galileo fallacy and denigration of scientific consensus." Think about that, "the denigration of scientific consensus." Strange that consensus means that everyone is in agreement at least to the point that they are willing to sign off on it. "It," in this case, may be the Big-Bang-Billions-of-Years-No-Flood-Molecules-to-Man story or "it" may be the Global Warming story. The two stories are not unrelated, since the Global Warming story assumes that Big-Bang-Billions-of-Years-No-Flood-Molecules-to-Man story. This "consensus" is achieved by eliminating anyone who openly disagrees. That is not a consensus. It is similar to the consensus that Mussolini achieved through fascism. In fact, it is a form of fascism where control is maintained by getting rid of anyone who voices opposition. So, it's not surprising that a person who refuses to acknowledge God would want to cover their tracks with a smoke screen on this one by creating a new fake-fallacy.
  • Four Terms Fallacy / Quaternio Terminorum occurs when a fourth term is introduced into a formal syllogism. This can also happen in informal logic, but it is harder to detect. If we think of a categorical syllogism, there must be three, and only three, terms. They must be unambiguous. The form is something like this: “All S are P. All S are M. All S are P.” Note that there are only three terms; S, P, and M. If the fallacy is committed, a fourth term is introduced. This is often done through equivocation. EXAMPLE “Nothing is more important than love. Crackers and cheese is better than nothing. Crackers and cheese is better than love.” That was easy, so it’s simple to see what happened. The word, “nothing,” has two meanings, so it introduces the fourth term. Love has several meanings and could fall into the same trap. EXAMPLE “Love fulfills all the Commandments. I want to love you tonight [They are not married.]. I want to fulfill all the Commandments tonight.” Actually, the second meaning of love doesn’t even have an overlap with the first meaning of love as the two are used in these statements. This is actually a common mistake with the word, “love,” though a syllogism is seldom used, and the logic is usually covered with innuendo or unstated. EXAMPLE “Science is observation. Evolution is observed. Therefore, Evolution is science.” It sounds good on the surface, and the logical form actually looks good. But let’s examine the reasoning: “Science is observation. Evolution [meaning any changes from generation to generation] is observed. Therefore, Evolution [meaning changes between families of living things such as felidea (cats), rodentia (rodents)] is science.” Now, we can see that it doesn’t make any sense.


Author/Compiler
Last updated: Sep, 2014
 
 


Formally Correct Fallacy / According to the Rules Fallacy (type of)

Logical Fallacy of Affirming the Consequent / Fallacy of the Undistributed Middle Term

Logical Fallacy of Commutation of Conditionals / Fallacy of the Consequent / Converting a Conditional

Logical Fallacy of Affirming a Disjunct / Fallacy of the Alternative Disjunct / False Exclusionary Disjunct / Affirming One Disjunct / Logical Fallacy of the Alternative Syllogism / Asserting an Alternative / Improper Disjunctive Syllogism / Fallacy

Logical Fallacy of Denying the Antecedent / Inverse Error / Fallacy of the Inverse / Invalid modus tollens

Logical Fallacy of Illicit Process

Logical Fallacy of Illicit Major

Logical Fallacy of Illicit Minor

Logical Fallacy of Invalid form using All

Logical Fallacy of Invalid form using "Some"

Logical Fallacy of Unwarranted Contrast / Some Are-Some Are Not

Logical Fallacy of Denying a Conjunct

Logical Fallacy of Negative Premise / Illicit Negative / Drawing a Positive Conclusion from Negative Premises

Logical Fallacy of Drawing a Negative Conclusion from Affirmative Premises / Illicit Affirmative

Logical Fallacy of Existential Instantiation / Existential Fallacy

Fallacy of Exclusive Premises

Logical Fallacy of Four Terms

Logical Fallacy of Necessity / Felacia Necassitas

Logical Fallacy of False Conversion / Illicit Conversion

Logical Fallacy of Illicit Contraposition

Formal Logical Fallacy Illicit Substitution of Identicals / Hooded Man Fallacy / Masked Man Fallacy / Intensional Fallacy / Epistemic Fallacy / Leibniz' Law Fallacy

Formal Logical Fallacy of Confusing "if" with "if and only if"

Logical Fallacy of Negating Antecedent and Consequent / Improper Transposition

Logical Fallacy of Invalid form using "OR"

Logical Fallacy of Confusion of "Necessary" with "Sufficient" Condition

Galileo Wannabe Fallacy / Galileo Argument (Formal)

Four Terms Fallacy / Quaternio Terminorum



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