for<p>

<center>
<tt>caused</tt> <i>F</i> <tt>if true</tt>
                         <tt>after</tt> <i>A</i> <tt>&</tt> <i>G</i>
</center>

<p>("there is a cause for <i>F</i> to hold after the execution of action
<i>A</i> in a state satisfying condition <i>G</i>").  The proposition<p>

<center>
<tt>nonexecutable</tt> <i>A</i> <tt>if</tt> <i>F</i>
</center>

<p>is shorthand for<p>

<center>
<tt>caused false if true after</tt> <i>A</i> <tt>&</tt> <i>F</i>.
</center>

<p>The proposition<p>

<center>
<i>A</i> <t