xliv.        Two wrongs make a right

The assertion that an action taken by a person is justified because another person would do the same in the same situation. Usually commensurate with an assessment of harm as a result of an action. It is important to note that it is not necessarily fallacious for one person to defend themselves again harm by performing an action similar to the intended course of action of another. But in many instances the justification is fallacious, since one wrong does not validate another when subjected to ethical consideration.

 

xliv.        Affirming the consequent

(or Asserting the consequent)

Affirming the consequent is a fallacy of Propositional Logic, with the following basic form:

If p then q.

q.

Ergo p.

(from Gary N Curtis’s Fallacy Files)

 

xlvi.        Denial of the antecedent

If p then q.

Not q

Therefore not p

The denial of the antecedent is based on an argument that a proposition is false because a consequent assertion is false. Unlike Non Causa Pro Causa, which is similar, but is fallacious in that p does not imply q, the Denial of the Antecedent is fallacious because the fact that the proposition q is false does not have a bearing on the falsehood of proposition p.
xlvii.       Converting a conditional

This fallacy is similar to the previous, Affirming the consequence, but that the proposition is framed in a conditional form.

If p then q, therefore if q then p.

Eg. “If educational standards are lowered, the quality of argument seen on the Internet worsens. So if we see the level of debate on the net get worse over the next few years, we’ll know that our educational standards are still falling.” (from The Atheism Web)

 

xlviii.     Complex question

Loaded question, fallacy of presupposition

The framing of a question so as to presuppose a particular answer, or a request for an explanation of an unproven fact.

Eg “Does the Chancellor plan two more years of ruinous privatization?” (From the Atheism web)
xlix.        Plurium Interrogationum

A demand for a simple answer to a complex question.

 

l.              Slippery Slope

An argument which asserts that one thing will plausibly lead to another, which will lead to another, etc.

(premises) A will/would lead to B, B will/would lead to C, …, Y will/would lead to Z.

(conclusion) A will/would lead to Z.

or

Event X has occurred, or will, or might occur

Therefore event Y will inevitably follow      (from the Nizkor website)
li.            Petitio principii

Begging the question – Circular reasoning

An argument which includes unproven assertions, or which includes a solution to the point in contention as a part of a conclusion on that issue. Where an argument draws upon its own conclusion to establish one of its premisses.

Nb. Circular arguments are surprisingly common, unfortunately. If you’ve already reached a particular conclusion once, it’s easy to accidentally make it an assertion when explaining your reasoning to someone else. (from The Atheism Web)

 

lii.           Circulus in demonstrando

Similar to Petitio principii. In this case, however, the conclusion is identical to a premise on which it is based, if worded differently.
liii.          Fallacy of Weak Analogy

An argument which asserts that since A and B have attributes a,b, and c in common, and A also has attribute z, B might reasonably be assumed to have attribute z.
liv.          Fallacy of Extended Analogy

The fallacy of extended analogy involves the assertion that two different instances considered in an argument about a general rule are analogous.

Eg. “I believe it is always wrong to oppose the law by breaking it.”

“Such a position is odious: it implies that you would not have supported Martin Luther King.”

“Are you saying that cryptography legislation is as important as the struggle for Black liberation? How dare you!” (genuine example taken from The Atheism Web)

 

lv.            Fallacy of anecdotal evidence

The fallacy of anecdotal evidence involves an assertion of personal experience or anecdote as proof. While anecdotal evidence can be compelling, particularly if an audience wants to accept a given conclusion, it cannot be offered alone as proof of a proposition.
lvi.          Non sequiter

Assuming a relationship between two unrelated events to establish an argument.
lvii.         Fallacy of Apriorism

Hasty generalisation

Using a single instance as the basis for establishing the truth of a general conclusion.

 

 

lviii.        Reification/Hypostatisation

The treatment of an abstraction as a concrete entity.

“I noticed you described him as ‘evil’. Where does this ‘evil’ exist within the brain? You can’t show it to me, so I claim it doesn’t exist, and no man is ‘evil’.” (From The Atheism Web)

 

 

lix.          Ad Hoc

An after the fact explanation, rather than a genuine argument. An Ad Hoc ‘argument’ explains a conclusion with reference to a specific instance mentioned, and does not apply to other situations.

Eg “I was healed from cancer.”

“Praise the Lord, then. He is your healer.”

“So, will He heal others who have cancer?”

“Er… The ways of God are mysterious.”

(from The Atheism Web)
lx.           Argumentum ad Logicam

The fallacy fallacy. The assertion of the falsehood of a proposition because it is based on a conclusion contrived through fallacious argument.
lxi.          Argumentum ad Nauseam

An argument which employs constant repetition based on the assertion that the more something is heard, the more likely it is to be true.