Philosophy Index

Henry M. Sheffer

Henry M. Sheffer (1882–1964) was an American logician, perhaps best known for the Sheffer stroke, a logical operator named in his honour.

Sheffer was born in Ukraine and came to the United States as a child. He studied philosophy at Harvard University, and spent most of his career as a professor there.

Sheffer stroke

In 1913, Sheffer showed that an alternative denial, otherwise known as a nand operation can be used to define every other truth-functional logical operator.

The symbol for the alternative denial ( |  or ↑) is known as the Sheffer stroke after Henry M. Sheffer.

Sheffer also demonstrated that an joint denial could be used for the same purpose, though Charles Sanders Peirce had also made the same discoveries in 1880, but his work was not published until 1933. The symbol for the joint denial ( ↓ ) is called the Peirce arrow.

The Sheffer stroke was used extensively by Bertrand Russell and W. V. O. Quine.


Name: Henry Maurice Sheffer
Born: 1882
Died: 1964