Confusion - exercise - satisfiable or valid I've the following exercise:

Determine if the following formula is satisfiable  or valid:
$P(x_{0}) \rightarrow \forall x_{1}P(x_{1})$


I've no idea what $P$ means, no information is given and my first thought is that if we define $P(x_{0}) := \ x_{0} \wedge \neg x_{0}$ then the formula is satisfiable, but if $P(x_{0}) := x_{0} \doteq c$ where $c$ is a constant then this is not true in general.
So from my point of view the answer depends on $P$.

How do I solve it? What is my problem?

$P$ is an arbitrary property. The sentence says that if $x_0$ has property $P$ then everything has property $P$. This is not universally true for all choices $P$ and $x_0$. But it is true for some choices of $P$ and $x_0$.
