  The problem of the self-interaction of a quasi-rigid classical particle with
an arbitrary spherically symmetric charge distribution is completely solved up
to the first order in the acceleration. No ad hoc assumptions are made. It is
shown that most of the puzzles that this problem has aroused are due to the
inertia of the negative pressure that equilibrates the electrostatic repulsion
inside the particle. When the inertia of pressure is taken into account the
dressed mass turns out to be the bare mass plus the electrostatic mass m=m_0 +
m_e. It is shown that a proper mechanical behaviour requires that m_0 > m_e/3.
This condition poses a lower bound on the radius that a particle of a given
bare mass and charge may have. The violation of this condition is the reason
why the Lorentz-Abraham-Dirac formula for the radiation reaction of a point
charge predicts unphysical motions that run away or violate causality. Provided
the mass condition is met the solutions of the exact equation of motion never
run away and conform to causality and energy and momentum conservation. When
the radius is much smaller than the wave-length of the radiated fields, but the
mass condition is still met, the exact expression reduces to the formula that
was advocated recently by Rohrlich.
