for Y being set
for T, R being Tolerance of (union Y) st ( for x, y being object holds
( [x,y] in T iff ex Z being set st
( Z in Y & x in Z & y in Z ) ) ) & ( for x, y being object holds
( [x,y] in R iff ex Z being set st
( Z in Y & x in Z & y in Z ) ) ) holds
T = R