# Ampheck

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- '''Ampheck''', from Greek {{polytonic|???????}} 'double-edged', is a term coined by [[Charles Sanders Peirce]] for either one of the pair of logically dual operators, variously referred to as [[Peirce arrow]]s, [[Sheffer stroke]]s, or [[logical NAND|NAND]] and [[logical NNOR|NNOR]]. Either of these logical operators is a [[sole sufficient operator]] for deriving or generating all of the other operators in what is variously called the subject matter of [[boolean function]]s, [[propositional calculus]], sentential calculus, or [[zeroth order logic]]. + '''Ampheck''', from Greek {{polytonic|???????}} 'double-edged', is a term coined by [[Charles Sanders Peirce]] for either one of the pair of logically dual operators, variously referred to as the [[logical NAND]] (or ''Sheffer stroke'') and the [[logical NNOR]] (or ''Peirce arrow''). Either of these logical operators is a [[sole sufficient operator]] for deriving or generating all of the other operators in what is variously called the subject matter of [[boolean function]]s, [[propositional calculus]], sentential calculus, or [[zeroth order logic]]. : For example, $x \bot y$ signifies that ''x'' is '''f''' and ''y'' is '''f'''. Then $( x \bot y ) \bot z$, or $\underline {x \bot y} \bot z$, will signify that ''z'' is '''f''', but that the statement that ''x'' and ''y'' are both '''f''' is itself '''f''', that is, is ''false''. Hence, the value of $x \bot x$ is the same as that of $\overline {x}$; and the value of $\underline {x \bot x} \bot x$ is '''f''', because it is necessarily false; while the value of $\underline {x \bot y} \bot \underline {x \bot y}$ is only '''f''' in case $x \bot y$ is '''v'''; and $( \underline {x \bot x} \bot x ) \bot ( x \bot \underline {x \bot x} )$ is necessarily true, so that its value is '''v'''. : For example, $x \bot y$ signifies that ''x'' is '''f''' and ''y'' is '''f'''. Then $( x \bot y ) \bot z$, or $\underline {x \bot y} \bot z$, will signify that ''z'' is '''f''', but that the statement that ''x'' and ''y'' are both '''f''' is itself '''f''', that is, is ''false''. Hence, the value of $x \bot x$ is the same as that of $\overline {x}$; and the value of $\underline {x \bot x} \bot x$ is '''f''', because it is necessarily false; while the value of $\underline {x \bot y} \bot \underline {x \bot y}$ is only '''f''' in case $x \bot y$ is '''v'''; and $( \underline {x \bot x} \bot x ) \bot ( x \bot \underline {x \bot x} )$ is necessarily true, so that its value is '''v'''.

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Ampheck, from Greek Template:Polytonic 'double-edged', is a term coined by Charles Sanders Peirce for either one of the pair of logically dual operators, variously referred to as the logical NAND (or Sheffer stroke) and the logical NNOR (or Peirce arrow). Either of these logical operators is a sole sufficient operator for deriving or generating all of the other operators in what is variously called the subject matter of boolean functions, propositional calculus, sentential calculus, or zeroth order logic.

For example, $x \bot y$ signifies that x is f and y is f. Then $( x \bot y ) \bot z$, or $\underline {x \bot y} \bot z$, will signify that z is f, but that the statement that x and y are both f is itself f, that is, is false. Hence, the value of $x \bot x$ is the same as that of $\overline {x}$; and the value of $\underline {x \bot x} \bot x$ is f, because it is necessarily false; while the value of $\underline {x \bot y} \bot \underline {x \bot y}$ is only f in case $x \bot y$ is v; and $( \underline {x \bot x} \bot x ) \bot ( x \bot \underline {x \bot x} )$ is necessarily true, so that its value is v.
With these two signs, the vinculum (with its equivalents, parentheses, brackets, braces, etc.) and the sign $\bot$, which I will call the ampheck (from Template:Polytonic, cutting both ways), all assertions as to the values of quantities can be expressed. (C.S. Peirce, CP 4.264).

In the above passage, Peirce introduces the term ampheck for the 2-place logical connective or the binary logical operator that is currently called the joint denial in logic, the NNOR operator in computer science, or indicated by means of phrases like 'neither-nor' or 'both not' in ordinary language. For this operation he employs a symbol that the typographer most likely set by inverting the zodiac symbol for Aries, but set above by commandeering the symbol for the bottom element of a lattice or partially ordered set.

In the same paper, Peirce introduces a symbol for the logically dual operator, rendered by the editors of CP by means of a bar or serif at the top of the inverted Aries symbol, in this way denoting the connective or operator that is currently called the alternative denial in logic, the NAND operator in computer science, or invoked by means of phrases like 'not-and' or 'not both' in ordinary language. It is not clear whether it was Peirce himself or later writers who initiated the practice, but on account of their dual relationship it became common to refer to these two operators in the plural, as the amphecks.

• Clark, Glenn (1997), "New Light on Peirce's Iconic Notation for the Sixteen Binary Connectives", pp. 304?333 in Houser, Roberts, Van Evra (eds.), Studies in the Logic of Charles Sanders Peirce, Indiana University Press, Bloomington, IN, 1997.
• McCulloch, W.S. (1961), "What Is a Number, that a Man May Know It, and a Man, that He May Know a Number?" (Ninth Alfred Korzybski Memorial Lecture), General Semantics Bulletin, Nos. 26 & 27, 7?18, Institute of General Semantics, Lakeville, CT, 1961. Reprinted, pp. 1?18 in Embodiments of Mind.
• McCulloch, W.S. (1965), Embodiments of Mind, MIT Press, Cambridge, MA.
• Peirce, C.S. (1902), "The Simplest Mathematics". First published as CP 4.227?323 in Collected Papers.
• Zellweger, Shea (1997), "Untapped Potential in Peirce's Iconic Notation for the Sixteen Binary Connectives", pp. 334?386 in Houser, Roberts, Van Evra (eds.), Studies in the Logic of Charles Sanders Peirce, Indiana University Press, Bloomington, IN, 1997.