There is a meme about Aristotle where "No one knows what this paragraph means", but no further details are given.
The passage in question is actually quite prosaic:
"One should observe these points closely, and in addition those corresponding to the perceptions that are necessary concomitants of the art of poetry. It is possible to make many mistakes with respect to these. But they have been discussed in sufficient detail in my published works."
It comes from Aristotle's Poetics, translated by Malcolm Heath. And the full footnote actually reads:
"No one knows what this paragraph means. By 'published works' Aristotle presumably means his On Poets."
Full context:
"8. OTHER ASPECTS OF TRAGEDY
8.1 Character
Enough has been said about the structure of events and what plots should be like; as for character, there are four things to aim at:
(i) First and foremost, goodness. As was said earlier, speech or action will possess character if it discloses the nature of a deliberate choice; the character is good if the choice is good. This is possible in each class of person: there is such a thing as a good woman and a good slave, even though one of these is perhaps deficient and the other generally speaking inferior.
(ii) Secondly, appropriateness: it is possible for the character to be courageous, but for this to be an inappropriate way for a woman to display courage or cleverness.
(iii) Thirdly, likeness: this is not the same as making character good and appropriate, as has already been stated.
(iv) Fourthly, consistency: even if the subject of the imitation is inconsistent, and that is the kind of character that is presupposed, it should nevertheless be consistently inconsistent.
An example of unnecessary badness of character is Menelaus in the Orestes; of impropriety and inappropriateness, Odysseus' lament in the Scylla and Melanippe's speech. An example of inconsistency is the Iphigeneia in Aulis: when she pleads for her life to be spared she is not at all like her later self - but in characterization, just as much as in the structure of events, one ought always to look for what is necessary or probable: it should be necessary or probable that this kind of person says or does this kind of thing, and it should be necessary or probable that this happens after that.
(Clearly, therefore, the resolutions of plots should also come about from the plot itself, and not by means of a theatrical device, as in the Medea, or the events concerned with the launching of the ships in the Iliad. A theatrical device may be used for things outside the play - whether prior events which are beyond human knowledge, or subsequent events which need prediction and narration - since we grant that the gods can see everything. But there should be nothing irrational in the events themselves; or, failing that, it should be outside the play, as for example in Sophocles' Oedipus.)
Since tragedy is an imitation of people better than we are, one should imitate good portrait-painters. In rendering the individual form, they paint people as they are, but make them better-looking. In the same way the poet who is imitating people who are irascible or lazy or who have other traits of character of that sort should por tray them as having these characteristics, but also as decent people. For example, Homer portrayed Achilles as both a good man and a paradigm of obstinacy.
One should observe these points closely, and in addition those corresponding to the perceptions that are necessary concomitants of the art of poetry. It is possible to make many mistakes with respect to these. But they have been discussed in sufficient detail in my published works."