Sheffer stroke

In the late 19th century and early 20th century, Charles Sanders Peirce and H.M. Sheffer independently discovered that a single binary logical connective suffices to define all logical connectives (they are each functionally complete). Two such connectives are

• $\uparrow$: the Sheffer stroke (sometimes denoted by $|$) and

• $\downarrow$: the Peirce arrow (sometimes denoted by $\perp$).

The Sheffer stroke is defined by the truth table

$P$	$Q$	$P\uparrow Q$
F	F	T
F	T	T
T	F	T
T	T	F

$Observethat$P↑Q$istrueifandonlyifeither$P$or$Q