user8157: In SN 12.17, it is said:

Well now, good Gotama, is suffering caused by oneself?
No indeed, Kassapa," said the Blessed One.
Well then, good Gotama, is one's suffering caused by another?
No indeed, Kassapa.
Well then, good Gotama, is suffering caused by both oneself and another?
No indeed, Kassapa.
'He who performs the act also experiences [the result]' — what you, Kassapa, first called 'suffering caused by oneself' — this amounts to
  the Eternalist theory. 
'One person performs the act, another experiences,' — which to the person affected seems like "suffering caused by another" — this
  amounts to the Annihilationist theory.

Alternate translation: 

Kassapa, if one thinks, ‘The one who acts is the same as the one who
  experiences the result,’ then one asserts with reference to one
  existing from the beginning: ‘Suffering is created by oneself.’ When
  one asserts thus, this amounts to eternalism. But, Kassapa, if one
  thinks, ‘The one who acts is one, the one who experiences the result
  is another,’ then one asserts with reference to one stricken by
  feeling: ‘Suffering is created by another.’ When one asserts thus,
  this amounts to annihilationism. Without veering towards either of
  these extremes, the Tathagata teaches the Dhamma by the middle: ‘With
  ignorance as condition, formations come to be; with
  volitional formations as condition, consciousness…. Such is the origin
  of this whole mass of suffering. But with the remainderless
  fading away and cessation of ignorance comes cessation of volitional
  formations; with the cessation of formations, cessation of
  consciousness…. Such is the cessation of this whole mass of
  suffering.’

Why are 'eternalism' & 'annihilationism' mentioned in SN 12.17 when SN 12.17 does not appear to be directly about reincarnation or about the denial of reincarnation? 

user10100: suffering caused by oneself=single relationship=easy to control=lord god=eternalism.
one's suffering caused by another=non relationship=hard to control=no avijjā&taṇhā to becoming/born=nihilism.
Those above all are impossible, so buddha taught paṭiccasamuppāda after denied acelaka kassapa's self view.

8157: <p>In <a href="http://www.accesstoinsight.org/tipitaka/sn/sn12/sn12.017x.wlsh.html" rel="nofollow noreferrer">SN 12.17</a>, it is said:</p>

<blockquote>
  <p><em>Well now, good Gotama, is suffering caused by oneself?</em></p>
  
  <p><em>No indeed, Kassapa," said the Blessed One.</em></p>
  
  <p><em>Well then, good Gotama, is one's suffering caused by another?</em></p>
  
  <p><em>No indeed, Kassapa.</em></p>
  
  <p><em>Well then, good Gotama, is suffering caused by both oneself and another?</em></p>
  
  <p><em>No indeed, Kassapa.</em></p>
  
  <p><em>'He who performs the act also experiences [the result]' — what you, Kassapa, first called 'suffering caused by oneself' — this amounts to
  the Eternalist theory.</em> </p>
  
  <p><em>'One person performs the act, another experiences,' — which to the person affected seems like "suffering caused by another" — this
  amounts to the Annihilationist theory.</em></p>
</blockquote>

<p><a href="https://suttacentral.net/en/sn12.17" rel="nofollow noreferrer">Alternate translation</a>: </p>

<blockquote>
  <p><em>Kassapa, if one thinks, ‘The one who acts is the same as the one who
  experiences the result,’ then one asserts with reference to one
  existing from the beginning: ‘Suffering is created by oneself.’ When
  one asserts thus, this amounts to eternalism. But, Kassapa, if one
  thinks, ‘The one who acts is one, the one who experiences the result
  is another,’ then one asserts with reference to one stricken by
  feeling: ‘Suffering is created by another.’ When one asserts thus,
  this amounts to annihilationism. Without veering towards either of
  these extremes, the Tathagata teaches the Dhamma by the middle: ‘With
  ignorance as condition, formations come to be; with
  volitional formations as condition, consciousness…. Such is the origin
  of this whole mass of suffering. But with the remainderless
  fading away and cessation of ignorance comes cessation of volitional
  formations; with the cessation of formations, cessation of
  consciousness…. Such is the cessation of this whole mass of
  suffering.</em>’</p>
</blockquote>

<p>Why are 'eternalism' &amp; 'annihilationism' mentioned in SN 12.17 when SN 12.17 does not appear to be directly about reincarnation or about the denial of reincarnation? </p>
 10100: <p>suffering caused by oneself=single relationship=easy to control=lord god=eternalism.</p>

<p>one's suffering caused by another=non relationship=hard to control=no avijjā&amp;taṇhā to becoming/born=nihilism.</p>

<p>Those above all are impossible, so buddha taught paṭiccasamuppāda after denied acelaka kassapa's self view.</p>
