  We propose a new mechanism to solve the fine-tuning problem. We start from a
multi-local action $
S=\sum_{i}c_{i}S_{i}+\sum_{i,j}c_{i,j}S_{i}S_{j}+\sum_{i,j,k}c_{i,j,k}S_{i}S_{j}S_{k}+\cdots$,
where $S_{i}$'s are ordinary local actions. Then, the partition function of
this system is given by \begin{equation} Z=\int d\overrightarrow{\lambda}
f(\overrightarrow{\lambda})\langle
f|T\exp\left(-i\int_{0}^{+\infty}dt\hat{H}(\overrightarrow{\lambda};a_{cl}(t))\right)|i\rangle,\nonumber\end{equation}
where $\overrightarrow{\lambda}$ represents the parameters of the system whose
Hamiltonian is given by $\hat{H}(\overrightarrow{\lambda};a_{cl}(t))$,
$a_{cl}(t)$ is the radius of the universe determined by the Friedman equation,
and $f(\overrightarrow{\lambda})$, which is determined by $S$, is a smooth
function of $\overrightarrow{\lambda}$. If a value of
$\overrightarrow{\lambda}$, $\overrightarrow{\lambda}_{0}$, dominates in the
integral, we can interpret that the parameters are dynamically tuned to
$\overrightarrow{\lambda}_{0}$. We show that indeed it happens in some
realistic systems. In particular, we consider the strong CP problem, multiple
point criticality principle and cosmological constant problem. It is
interesting that these different phenomena can be explained by one mechanism.
