This sentence was not said by Irving Stone, but by John Sheffield.

The original words are:

Love is the salt of life; a higher taste it gives to Pleasure, and then makes it last.

John Sheffield is a nobleman , his full name is: Buckingham and Normanby, John Sheffield, 1st Duke of, 3RD EARL OF MULGRAVE Buckingham and Normanby Duke (first generation)

So it is sometimes referred to as Buckingham.