Full Idea
Aristotle's discussion of the unmoved mover and of the soul confirms the suspicion that form, when it is not thought of as the object represented in a definition, plays the role of the ultimate mereological atom within his system.
Clarification
'Mereology' concerns how parts make up wholes
Gist of Idea
The unmoved mover and the soul show Aristotelian form as the ultimate mereological atom
Source
report of Aristotle (works [c.330 BCE]) by Kathrin Koslicki - The Structure of Objects 6.6
Book Reference
Koslicki,Kathrin: 'The Structure of Objects' [OUP 2008], p.162
A Reaction
Aristotle is concerned with which things are 'divisible', and he cites these two examples as indivisible, but they may be too unusual to offer an actual theory of how Aristotle builds up wholes from atoms. He denies atoms in matter.