Tandem-wing Airplanes

Here's another question for you engineers out there. Traditional
airplane design has the tail pressing down, so the tail is fighting
the work that the main wing is doing. A tandem-wing airplane in which
both front and rear wings are lifting upward is a more efficient
design, which is one reason Bert Rutan chose the canard configuration
for so many of his designs. But in the canard configuration, the
front wing is smaller than the rear wing. This is what I don't
understand. It seems to me that a design in which the front wing was
larger and the rear wing was smaller would be more stable in pitch.
The smaller rear wing would automatically damp pitch excursions like
the fins of an arrow. So why is the canard the most successful tandem-
wing design flying?