Passage adapted from Samuel Johnson, "Preface to Shakespeare (1756)," 9-63, in Johnson on Shakespeare: Essays and Notes Selected and Set Forth with an Introduction by Walter Raleigh (London: Oxford University Press, 1969): 29.

"Whether Shakespeare knew the unities, and rejected them by design, or deviated from them by happy ignorance, it is, I think, impossible to decide, and useless to enquire. We may reasonably suppose, that, when he rose to notice, he did not want the counsels and admonitions of scholars and criticks, and that he at last deliberately persisted in a practice, which he might have begun by chance."

Which of the following is NOT one of the "unities" alluded to in the above excerpt?