Zeroth order logic

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Zeroth order logic is an informal term that is sometimes used to indicate the common principles underlying the algebra of sets, boolean algebra, boolean functions, logical connectives, monadic predicate calculus, propositional calculus, and sentential logic.  The term serves to mark a level of abstraction in which the more inessential differences among these subjects can be subsumed under the appropriate isomorphisms.
==Propositional forms on two variables==
By way of initial orientation, Table 1 lists equivalent expressions for the sixteen functions of concrete type X \times Y \to \mathbb{B} and abstract type \mathbb{B} \times \mathbb{B} \to \mathbb{B} in a number of different languages for zeroth order logic.
 Table 1. Propositional Forms on Two Variables
L1 	L2 	L3 	L4 	L5 	L6
 	x : 	1 1 0 0	  	  	 
 	y : 	1 0 1 0	  	  	 
f0 	f0000	0 0 0 0	( ) 	false 	0
f1 	f0001	0 0 0 1	(x)(y) 	neither x nor y 	¬x ∧ ¬y
f2 	f0010	0 0 1 0	(x) y 	y and not x 	¬x ∧ y
f3 	f0011	0 0 1 1	(x) 	not x 	¬x
f4 	f0100	0 1 0 0	x (y) 	x and not y 	x ∧ ¬y
f5 	f0101	0 1 0 1	(y) 	not y 	¬y
f6 	f0110	0 1 1 0	(x, y) 	x not equal to y	x ≠ y
f7 	f0111	0 1 1 1	(x y) 	not both x and y	¬x ∨ ¬y
f8 	f1000	1 0 0 0	x y 	x and y 	x ∧ y
f9 	f1001	1 0 0 1	((x, y))	x equal to y 	x = y
f10 	f1010	1 0 1 0	y 	y 	y
f11 	f1011	1 0 1 1	(x (y)) 	not x without y 	x → y
f12 	f1100	1 1 0 0	x 	x 	x
f13 	f1101	1 1 0 1	((x) y) 	not y without x 	x ← y
f14 	f1110	1 1 1 0	((x)(y))	x or y 	x ∨ y
f15 	f1111	1 1 1 1	(( )) 	true 	1
These six languages for the sixteen boolean functions are conveniently described in the following order:
* Language L3 describes each boolean function f : B2 → B by means of the sequence of four boolean values (f(1,1), f(1,0), f(0,1), f(0,0)). Such a sequence, perhaps in another order, and perhaps with the logical values F and T instead of the boolean values 0 and 1, respectively, would normally be displayed as a column in a truth table.
* Language L2 lists the sixteen functions in the form fi, where the index i is a bit string formed from the sequence of boolean values in L3.
* Language L1 notates the boolean functions fi with an index i that is the decimal equivalent of the binary numeral index in L2.
* Language L4 expresses the sixteen functions in terms of logical conjunction, indicated by concatenating function names or proposition expressions in the manner of products, plus the family of minimal negation operators, the first few of which are given in the following variant notations:
: \begin{matrix}
(\ ) & = & 0 & = & \mbox{false} \\
(x) & = & \tilde{x} & = & x' \\
(x, y) & = & \tilde{x}y \lor x\tilde{y} & = & x'y \lor xy' \\
(x, y, z) & = & \tilde{x}yz \lor x\tilde{y}z \lor xy\tilde{z} & = & x'yz \lor xy'z \lor xyz'
\end{matrix}
It may also be noted that (x, y)\! is the same function as x + y\! and x \ne y, and that the inclusive disjunctions indicated for (x, y)\! and for (x, y, z)\! may be replaced with exclusive disjunctions without affecting the meaning, because the terms disjoined are already disjoint. However, the function (x, y, z)\! is not the same thing as the function x + y + z\!.
* Language L5 lists ordinary language expressions for the sixteen functions. Many other paraphrases are possible, but these afford a sample of the simplest equivalents.
* Language L6 expresses the sixteen functions in one of several notations that are commonly used in formal logic.
==Translations==
* 中文 : 零阶逻辑
==Syllabus==
===Focal nodes===
* Inquiry Live
* Logic Live
===Peer nodes===
* Zeroth Order Logic @ InterSciWiki
* Zeroth Order Logic @ MyWikiBiz
* Zeroth Order Logic @ Subject Wikis
* Zeroth Order Logic @ Wikiversity
* Zeroth Order Logic @ Wikiversity Beta
===Logical operators===
* Exclusive disjunction
* Logical conjunction
* Logical disjunction
* Logical equality
* Logical implication
* Logical NAND
* Logical NNOR
* Negation
===Related topics===
* Ampheck
* Boolean domain
* Boolean function
* Boolean-valued function
* Differential logic
* Logical graph
* Minimal negation operator
* Multigrade operator
* Parametric operator
* Peirce's law
* Propositional calculus
* Sole sufficient operator
* Truth table
* Universe of discourse
* Zeroth order logic
===Relational concepts===
* Continuous predicate
* Hypostatic abstraction
* Logic of relatives
* Logical matrix
* Relation
* Relation composition
* Relation construction
* Relation reduction
* Relation theory
* Relative term
* Sign relation
* Triadic relation
===Information, Inquiry===
* Inquiry
* Dynamics of inquiry
* Semeiotic
* Logic of information
* Descriptive science
* Normative science
* Pragmatic maxim
* Truth theory
===Related articles===
* Cactus Language
* Futures Of Logical Graphs
* Propositional Equation Reasoning Systems
* Differential Logic : Introduction
* Differential Propositional Calculus
* Differential Logic and Dynamic Systems
* Prospects for Inquiry Driven Systems
* Introduction to Inquiry Driven Systems
* Inquiry Driven Systems : Inquiry Into Inquiry
==Document history==
Portions of the above article were adapted from the following sources under the GNU Free Documentation License, under other applicable licenses, or by permission of the copyright holders.
* Zeroth Order Logic, InterSciWiki
* Zeroth Order Logic, MyWikiBiz
* Zeroth Order Logic, PlanetMath
* Zeroth Order Logic, Wikinfo
* Zeroth Order Logic, Wikiversity
* Zeroth Order Logic, Wikiversity Beta
* Zeroth Order Logic, Wikipedia
* Zeroth Order Logic, Altheim.com
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