# Controversial Logic

#### Turtle

"Controversial" Logic

I need to do something "controversial" for a report, so what in logic is controversial?

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#### Mentat

By "controversial", do you mean something that Logicians don't agree on?

#### ahrkron

Staff Emeritus
Gold Member
You can probably talk about non-monotonic logics used for artificial intelligence (haven't heard about them in a while... I don't know if there are still people working on this).

Other possible topic: quantum logic, fuzzy logic, paraconsistent logic.

#### Sunfist

What about the logic that "proves" that God exists like the Ontalogical(sp) argument?

#### FZ+

The logic of how logic arose?

#### caumaan

That is actually a very good point. Who decides logic or reason? Why does people agreeing on something make it logical?

#### quartodeciman

The logic that has revived ontological arguments is called modal logic. There are four regular divisions of modal logic:

1. alethic - about possible and necessary truth/falsity
2. deontic - about permissibility and obligation
3. temporal - about past and future truth/falsity
4. doxastic - about neutrality and belief

. Special operators are added to standard logic connectives and quantifiers to enable modal expressions. In some of these divisions, formal duality is explored.

Ontological arguements have always seemed to me to reduce to arguments of the form "If an ultimate being exists, then it exists indubitably." The trick has always been to load up the meaning of the "ultimate being" from the beginning, and then to express the conclusion unconditionally (UB exists. QED. Amen)
The alethic modal form of ontological argument does a most clever job of hiding this in its postulates, and tends to look like a standard formal logic proof, using general theorems and arriving at the conclusion in step-by-step fashion. But the minor premise (UB might possibly exist) is still a given in the argument, so the argument still comes under the usual form.

Modal logics are modeled (represented) in two ways: actually and possibly. Actualism maintains that all objects are actually existent objects in one real universe; possibilism maintains that objects are possible beings in logically consistent possible universes.

http://plato.stanford.edu/entries/logic-modal
modal logic

http://cs.wwc.edu/KU/Logic/Modal.html [Broken]
modal logics

http://www.earlham.edu/~peters/courses/re/onto-arg.htm
the ontological argument

quart

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#### laserblue

The 22nd and 24th presidents of the United States have the same mother and father but are not brothers. How can this be so?

#### NateTG

Homework Helper
Obviously there's the Incompleteness theorem.

A more recent controversy would be computer proofs and the 4 color theorem.

You can also do a report on falacious arguments, and if you don't get enough controversy use ontological arguments as examples.

#### phoenixthoth

The 22nd and 24th presidents of the United States have the same mother and father but are not brothers. How can this be so?
i don't know, they're the same person? they're sisters? their mother and father is God? ;)

well set theory can be kinda contraversial, which kinda smells like logic. i think the most contraversial axiom is the axiom of choice. it proves certain things that some people don't like such as:
1. a nonmeasurable set
2. the banach-tarski theorem which says that a sphere one inch in diameter can be chopped into five pieces and rearranged into a life-size statue of jesus christ. i guess some people don't like the fact that volume is not conserved under finitely many choppings.

i think some people also choose to not accept the power set axiom, that the *** of all subsets of a given set is a set.

i guess this also reminds me of non-euclidean geometry.

i don't know whether the statement "logic should be tossed in the trash and fuzzy logic put in its place" is contraversial or not.

#### Yahweh

Originally posted by laserblue
The 22nd and 24th presidents of the United States have the same mother and father but are not brothers. How can this be so?
The 22nd and 24th presidents were in fact the same person, Grover Cleaveland.

#### Yahweh

Originally posted by FZ+
The logic of how logic arose?
Our old buddy lifegazer began a thread on the JREF boards called Origins of reason. (He went off on a tangent of "where does logic come from if it doesnt already exist" or something like that...)

He asked where reason and logic came from, I gave him this response:
Ultimate origins of "reason":
Trial and error, observation and experience.

[Rest of post truncated as it is unnecessary]
No mysteries in the logic of how logic arose (the reasoning is due to the fact that the origin of logic is not a Philosophical question, instead its better rooted in the natural evolution of knowledge).

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