Apart from the apparently rushed handwriting, the notebook is difficult to translate... the ferocious of the sentences sees them running at angles to the lines of the page, or disappearing into the margins. The jumps between subjects - although they all rotate around an unexpressed theory of theatre - occludes any systematic meaning.
Aristotle provides a template for the analysis of 'the theatrical experience'
is followed by half a blank page, then a change of pen
founded on mimesis - particular
form and content
genre is an instrument to assess the reasons for effectiveness and not the measure of effectiveness
tragic - epic - history - rhetoric
Perhaps this is an attempt to decode Aristotle's use of genre as a hierarchy: tragedy is the highest form (because, per Aristotle, it is the closest to philosophy), and rhetoric, the lowest.
'music' (is philosophy a genre? it is presented as 'a good', since the virtue of poetry is in its closeness to 'universals' and therefore philosophy)
Of course, when Aristotle talks about 'universals', it mean something akin to Plato's forms. This might be in contrast to the idea of 'universality' that is sometimes identified as the finest quality in art (that it transcends its temporal context and points to some absolute of the human condition). Diderot, conversely, sees those plays, like his own, that deal with specific ideas (like, say, fatherhood) are more likely to achieve this universality. That is despite these plays being very concerned with the immediate debates around the idea in question.
Tragedy's value is educational... (probably need to ask what counts as 'education' - at least, implied 'good education'