  In this paper we consider iterated integrals on
$\mathbb{P}^{1}\setminus\{0,1,\infty,z\}$ and define a class of
$\mathbb{Q}$-linear relations among them, which arises from the differential
structure of the iterated integrals with respect to $z$. We then define a new
class of $\mathbb{Q}$-linear relations among the multiple zeta values by taking
their limits of $z\rightarrow1$, which we call \emph{confluence relations}
(i.e., the relations obtained by the confluence of two punctured points). One
of the significance of the confluence relations is that it gives a rich family
and seems to exhaust all the linear relations among the multiple zeta values.
As a good reason for this, we show that confluence relations imply both the
regularized double shuffle relations and the duality relations.
