Definition:Set Intersection/Historical Note

Historical Note on Set Intersection

The concept of set intersection, or logical multiplication, was stated by Leibniz in his initial conception of symbolic logic.

The symbol $\cap$, informally known as cap, was first used by Hermann Günter Grassmann in Die Ausdehnungslehre from $1844$.

However, he was using it as a general operation symbol, not specialized for set intersection.

It was Giuseppe Peano who took this symbol and used it for intersection, in his $1888$ work Calcolo geometrico secondo l'Ausdehnungslehre di H. Grassmann.

Peano also created the large symbol $\bigcap$ for general intersection of more than two sets.

This appeared in his Formulario Mathematico, 5th ed. of $1908$.

Sources

• 1992: George F. Simmons: Calculus Gems ... (previous) ... (next): Chapter $\text {A}.19$: Leibniz ($\text {1646}$ – $\text {1716}$)

• Earliest Uses of Symbols of Set Theory and Logic in Jeff Miller's website Earliest Uses of Various Mathematical Symbols