-hereditary property belonging to
. These definitions can all be applied to any other relation just as well as to
. Thus if
is any relation whatever, we can lay down the following definitions:[8]—
[8]These definitions, and the generalised theory of induction, are due to Frege, and were published so long ago as 1879 in his Begriffsschrift. In spite of the great value of this work, I was, I believe, the first person who ever read it—more than twenty years after its publication.
A property is called "