Full Idea
Aristotle distinguishes between deductive reasoning (sullogismos) and demonstration (apodeixis). All demonstration is deductive reasoning, but not all deductive reasoning is demonstration.
Gist of Idea
There is pure deductive reasoning, and explanatory demonstration reasoning
Source
report of Aristotle (Posterior Analytics [c.327 BCE], Bk I.2) by Vassilis Politis - Aristotle and the Metaphysics 5.3
Book Reference
Politis,Vasilis: 'Aristotle and the Metaphysics' [Routledge 2004], p.130
A Reaction
This sounds not far off the distinction between single-turnstile (formal proof) and double-turnstile (semantic consequence). Politis says, though, that the key point is the demonstration is explanatory.