A commos is a song of lament shared by the chorus and the actors on the stage. The constituent parts to be used as ingredients of tragedy have been described above; these are the separable members into which it is quantitatively divided. The whole of chapter 12. bears marks of belonging to the Poetics but seems out of place, since it interrupts the discussion of plot. Following upon what has been said above we should next state what ought to be aimed at and what avoided in the construction of a plot, and the means by which the object of tragedy may be achieved. Since then the structure of the best tragedy should be not simple but complex See chapter 10. and one that represents incidents arousing fear and pity—for that is peculiar to this form of art—it is obvious to begin with that one should not show worthy men passing from good fortune to bad. That does not arouse fear or pity but shocks our feelings. Nor again wicked people passing from bad fortune to good. That is the most untragic of all, having none of the requisite qualities, since it does not satisfy our feelings i.e., our preference for poetic justice. or arouse pity or fear.