[Jellby]

Argh! Don't use a list for what is not a list at all, please. It might end up looking the way you want, but so can anything with proper styling.

I recommend something like:

div.poetry {
  margin: 1em 0 1em 2em;
}
div.stanza { 
  margin: 0.5em 0;
  page-break-inside: avoid;
} 
div.poetry p {
  margin: 0;
  padding-left: 5em;
  text-indent: -5em; 
  text-align: left;
} 
div.poetry p.indented {
  margin-left: 1.5em;
}

<div class="poetry">

<div class="stanza">
<p>"You are old, Father William," the young man said,</p>
<p class="indented">"And your hair has become very white;</p>
<p>And yet you incessantly stand on your head—</p>
<p class="indented">Do you think, at your age, it is right?"</p>
</div>

<div class="stanza">
<p>"In my youth," Father William replied to his son,</p>
<p class="indented">"I feared it might injure the brain;</p> 
<p>But, now that I'm perfectly sure I have none,</p>
<p class="indented">Why, I do it again and again."</p>
</div>

</div>

Or you can replace the <p> inside the <div class="poetry"> with <div>, or <div class="line">...