HTML CODES FOR LOGIC

COMBINED FROM VARIOUS INTERNET SITES

 Arranged by Description 

DESCRIPTION

SYMBOL

HTML DEC. NO.

And (G)

∙

And (H)

∧

Approx

≈

Assertion

⊦

Bicondidional (G)

≡

Biconditional (H)

⇔

Dagger, Nor

↓

Degree

°

°

Element of

∈

Empty Set

∅

Exist Quantifier

∃

Implication (G)

⊃

Implication (H)

→

Includes

⊂

Infinity

∞

Intersection

∩

L R Arrow single

↔

Necessity

◻

Negation (G)

∼

Negation (H)

¬

¬

Or

∨

Plus-minus

±

±

Possibility

⋄

Proportional

∝

Rt to L Arrow

←

Square Root

√

Star

⋆

Stroke, Nand

|

|

Therefore

∴

Union

∪

Univ Quantifier

∀

 

Arranged by HTML Decimal Code Numbers

HTML DEC. NO.

DESCRIPTION

SYMBOL

|

Stroke, Nand

|

¬

Negation (H)

¬

°

Degree

°

±

Plus-minus

±

←

Rt to L Arrow

→

Implication (H)

↓

Dagger, Nor

↔

L R Arrow single

⇔

Biconditional (H)

∀

Univ Quantifier

∃

Exist Quantifier

∅

Empty Set

∈

Element of

∙

And (G)

√

Square Root

∝

Proportional

∞

Infinity

∧

And (H)

∨

Or

∩

Intersection

∪

Union

∴

Therefore

∼

Negation (G)

≈

Approx

≡

Bicondidional (G)

⊂

Includes

⊃

Implication (G)

⊦

Assertion

⋄

Possibility

⋆

Star

◻

Necessity

 As everyone knows, there are many different systems of logical notation.  I've included the symbols that would most frequently come up in anything I might post on-line. For word-processing or other applications, there are different codes for inserting them. E.g., in MS-Word you can get them from the symbols collection conveniently located under "Symbols" on the "Insert" ribbon.

I've included the symbols for the two systems that I have used most frequently over the last few years, the ones used by Harry Gensler in Introduction to Logic, 2nd ed. (Routledge, 2010) and by Colin Howson in his book, Logic with Trees (Routledge, 1997). Where these two systems have two different symbols for one expression, I've distinguished them with the letters (G) and (H) respectively.

If you don't do HTML very much, you need to know that these codes reproduce the symbol in full, just like " " creates a hard space. The "&," "#," and ";" are necessary.  

Let's say you're setting up an argument with several premises and a conclusion. Obviously I wouldn't think of typing out each code each time it comes up, I suggest that you write out all of the lines and just ignore the symbols that aren't standard on your keyboard. When you're done with your basic set up, you can then copy all of the codes in turn from the list and paste them in all the places where they belong. Or, if you are using an editor, and you have copied the code once into the HTML source, you can copy and paste the symbol everywhere else in the wysiwig view. In some cases, you'll probably want to leave a space before and after the code.

Here's an example, with a nod to the author you can always count on to cheer you up, Fyodor Dostoyevski. (Thus, this is not the St. Pete's in Florida.) Normally, you'd fill out all of the spaces on the basic framework you've constructed, and not do it in separate lines, which I'm just doing for illutrative purposes. I'll use Gensler's symbols, but add a universal quantifier symbol just for fun.

"If all novelists write in St. Petersburg, then necessarily some readers are patient."

( x)(Nx   Sx) ( x)(Rx  Px)

( x)(Nx   Sx) ( x)(Rx  Px)

(∀x)(Nx   Sx)  ( x)(Rx  Px)

(x)(Nx Rx)   ( x)(Rx  Px)

(∀x)(Nx  ⊃ Sx) ⊃ ( x)(Rx   Px)

(x)(Nx Rx) ( x)(Rx Px)

(∀x)(Nx ⊃ Sx) ⊃ ◻( x)(Rx Px)

(x)(Nx Rx) ( x)(Rx Px)

(∀x)(Nx ⊃ Sx) ⊃ ◻(∃x)(Rx Px) 

(x)(Nx Rx) (x)(Rx Px)

(∀x)(Nx ⊃ Sx) ⊃ ◻(∃x)(Rx ∙ Px)

 (x)(Nx Rx) ⊃ ◻(x)(Rx Px)

So, to put the sentence and the translation together:

If all novelists write in St. Petersburg, then necessarily some readers are patient.

((x)(Nx Rx) ⊃ ◻(x)(Rx Px))

To follow Gensler's style accurately, I have to enclose the entire wff with parentheses. Any truth-functional relationship of propositions gets set apart like that. At first, seems like a needless bother, but gets pretty helpful in working through more complex propositions. It also helps you keep track of the fact that just because two letters are connected, they are not necessarily propositions and then they would not stand in a truth-functional relationship. E.g. you have

(A ⊃ B)

A implies B.

but

~a=b

Constant a is not identical with constant b.

 

By the way, there may still be some people who are not aware of Fr. Gensler's logic book and his fabulous software system, Logicola, which one can download for free from his website. His is by far the best intro text in logic these days. It is extremely easy for instructors to adapt to their needs. In my last ten years or so of teaching from it (out of a total of about 25 years counting its predecessors), due to the caliber of students I had, we wound up going from propositional logic right up to modal systems and quantified modal in one semester.

 

Howson's book is an intriguing alternative, which I've used with advanced students. Its style is radically different.  It uses the "truth-tree" approach to proofs and covers a number of different topics, some of which have mathematical analogies. For example, he includes logical induction on predecessors and then also shows how mathematical induction works (neither of which, by the way, has anything to do with "inductive logic").

If you know of a wysiwyg editor that already includes all of these symbols, I'd appreciate hearing about it.  Also, I imagine it's possible to make up short-cut macros, though I'm not sure it's worth the trouble. Copying and pasting works pretty well. But again, if you've worked out something useful, I'd love to hear from you.  

Hope that all your arguments are sound.

Back to my blog.

Collected by Win Corduan

September 7, 2011