This really applies to any work of art not just the classics that we cannot appreciate it if it is completely explained to us. We may need some guidance about the context or the assumptions about the artist and some hints about the right direction to take but we have to grasp it ourselves and to fill in the gaps for ourselves.where the artist is silent. Demetrius here quotes Theophrastus making a similar point.
Ἐν τούτοις τε οὖν τὸ πιθανόν, καὶ ἐν ᾧ Θεόφραστός φησιν, ὅτι οὐ πάντα ἐπ̓ ἀκριβείας δεῖ μακρηγορεῖν, ἀλλ̓ ἔνιακαταλιπεῖν καὶ τῷ ἀκροατῇ συνιέναι, καὶ λογίζεσθαι ἐξ αὑτοῦ: συνεὶς γὰρ τὸ ἐλλειφθὲν ὑπὸ σοῦ οὐκ ἀκροατὴς μόνον, ἀλλὰκαὶ μάρτυς σου γίνεται, καὶ ἅμα εὐμενέστερος. συνετὸς γὰρἑαυτῷ δοκεῖ διὰ σὲ τὸν ἀφορμὴν παρεσχηκότα αὐτῷ τοῦσυνιέναι, τὸ δὲ πάντα ὡς ἀνοήτῳ λέγειν καταγινώσκοντιἔοικεν τοῦ ἀκροατοῦ.
These, then, are the main essentials of persuasiveness; to which may be added that indicated by Theophrastus when he says that all possible points should not be punctiliously and tediously elaborated, but some should be left to the comprehension and inference of the hearer (Theophrastus Peri Lexeôs), who when he perceives what you have omitted becomes not only your hearer but your witness, and a very friendly witness too. For he thinks himself intelligent because you have afforded him the means of showing his intelligence. It seems like a slur on your hearer to tell him everything as though he were a simpleton.
Demetrius On Style 222
Translation William Rhys Roberts