<p><pre><code>     the conflict between the &quot;machine model&quot;  ...
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I&#x27;m not sure I can agree. The original post makes the point that you can see recursion in multiple ways, including machine-oriented (e.g. using a stack and stack pointer) and abstract, e.g. using an axiomatisation of self-reference, for example using the Y combinator which satisfies YM = M(YM).<p>Incidentally, stacks can also be given an axiomatic treatment indepented of concrete machine models.