Prolog clause terminates individually, but not together
<p>So</p>

<pre><code>?- canCall(mary, Person).
</code></pre>

<p>works and terminates and</p>

<pre><code>?- canFind(mary, Person).
</code></pre>

<p>also works and terminates. But somehow </p>

<pre><code>?- canCall(mary, Person), canFind(mary, Person). 
</code></pre>

<p>does not terminate. What may be a possible reason?</p>