  Let $T\dopu C(S)\to C(S)$ be a bounded linear operator. We present a
necessary and sufficient condition for the so-called Daugavet equation $$
\|\Id+T\| = 1+\|T\| $$ to hold, and we apply it to weakly compact operators and
to operators factoring through $c_{0}$. Thus we obtain very simple proofs of
results by Foias, Singer, Pelczynski, Holub and others.
