Robert A. Markus died of cancer in 2010, at the age of 86. Together with Peter Brown (who cites Markus often in his own works, and contributed the Epilogue to Markus’ Festschrift), Markus was responsible for fleshing-out the territory of the study of Late Antiquity — generously speaking, between Imperial Rome in the third century A.D. and Charlemagne.
Of Romanian Jewish parents (who left Romania in 1939, settling eventually in England), yet later a convert to Catholicism, Markus studied medieval philosophy at Manchester University together with figures like Alasdair MacIntyre, had a stint as a Dominican, and then settled down to marry. He taught at Liverpool, then at Nottingham, taking early (though quite active) retirement.
Saeculum: History and Society in the Theology of St. Augustine, Revised Edition (New York: Cambridge, 2007) was his first significant book (a helpful list of Markus’ publications can be found here). Originally published in 1970, it was eventually revised for a second edition. Markus’ thesis in Saeculum is only slightly slippery: whether we claim (with Thomas M. Parker) that its center is found in “Augustine’s conception of the relation between sacred and secular history”, or in “Augustine’s secularization of political institutions” and his “views on the nature and purpose of human society” (John Dillon), we still come very close to the heart of the book. (The subtitle “History and Society” should suggest as much, since the pair is related, but not totally unified.) In a manner, these senses may be reconciled in Gerard A. Reed’s review, where the book’s heart is to be found in “Augustine consider[ing] [that] Christian society [is] eschatological rather than terrestrial, rejecting any socio-political notions which denied the non-temporal, trans-historical dimensions of his City of God”, though, despite this eschatological acknowledgement, the crux of the book is in the way that Augustine secularized conceptions of history, society (including the “state”), and the Church, by evaluating them all through this-worldly terms and/or ends. The chapters that follow flesh this out.
Here, Markus offers some “reflections on the first edition of this book.” [ix] He begins by tracing back lines from Augustine’s later political thought to his work, De Doctrina Christiana (usually translated as “On Christian Doctrine”, here abbreviated DDC). The DDC considered the “customs, rites, arrangements, arts, and disciplines in use among men” as “institutions”, some “human”, some “demonic.” Demonic institutions largely deal with signing-conventions by which demons are engaged, and which are constructed in commerce with them (principally, sacrifice). Human institutions are “the media of human communication”, and built by convention. Some human institutions are superfluous, some are “useful and necessary, the arts and practices without which the harmonious functioning of society would be impaired.” [ix]
“From the outset, one important purpose of the City of God [De Civitate Dei Contra Paganos, the “On the City of God Against the Pagans”, here simply CoG] was to meet the anxieties of high pagan imperial functionaries who found it difficult to understand how Christians could give full weight to the claims upon them of obligations toward the civil community.” [xi] Augustine set out to “define the nature of a civil community in a way such as would justify the claims of the Empire to the full loyalty of Christian no less than pagan Romans.” [xii] Pagans needed “to be reassured […] that the social and political implications of the Gospel did not undermine patriotic loyalties.” Still, the “image of the social order” subsequently painted in the CoG offers a model of society full of unresolvable conflict, tension, and “value-systems”. (Instead of resolving differences, or finding a higher secular ground between them, Augustine’s secularity offered a model in which the differences remained.)
“St. Paul had impressed on Augustine’s mind a graphic image of a self divided against itself”. [xiii] This “dislocation […] results from and reflects the dislocation in the primordial community between man and God.” [xiv] “The divided self is Augustine’s model of the dislocation of all human life.” Nature and society are alienated from humanity. The divisions are unnatural, brought about through pride, and restored by grace. “Community is the proper form and final goal of human living together, and charity between men its essential condition; yet, every attempt of human beings to live together in concord is foiled. The structures of communication turn, with a grim inevitability, into means of domination, sharing into exploitation, concord into conflict.” [xv]
The monastic community is an exception of this. Though sin infects her, too, she is not a community formed by necessity, but entered into and affiliated with voluntarily, and founded on mutual love, led by “a father whose authority was a service of love, not domination (libido dominandi) which corrupts all other forms of society.” [xvi] Domination is the key to this dislocation in Augustine: “[t]he lust for domination is perverse imitation of God, rooted in pride, from which all sin springs.” [xvii] Pride is privative; its antidote is “charity, which seeketh not its own” [xviii]. Indeed
[p]erverse self-love, rooted in pride, is the basic disorder in the human self and the basic force disruptive in society: it isolates the self from community with its fellows. ‘Private’ and ‘sociable’ are two fundamentally opposed forms of loving: the one enclosing the self in its own narrowness, the other setting it free in sharing with others. These are the two opposed ‘loves’ which define the earthly and the heavenly Cities: the heavenly City is structured by mutual love and sharing, the earthly by ‘possessive individualism’. [xviii]
“In Augustine’s mature view of society the purpose of political arrangements was to contain the disorder and the tensions inevitably present in any society of sinful men.” Government can be infected by the “vice” and factional evil it is to contain, however. [xix] The CoG “resists […] the divinisation of any form of social arrangement.” [xx] Despite this, we must “dedicate ourselves to the pursuit of a justice we know to be unattainable here: to a quest which is doomed, and yet, is an inescapable duty.”
In “the first place”, Saeculum is “a historical study” about “the fundamentals of the way in which Augustine conceived the social dimension of human, especially Christian, existence.” [xxi] “How did he think of actual, historical societies –particularly of the ‘state’ of his own day, the Roman Empire– in relation to the whole history of human societies? What, in the end, did he consider to be man’s right posture in the saeculum: the world of men and of time?” [xxii] “In the second place”, this investigation “carv[es] a channel” from Augustine to our own times, because historical investigation is a “two-way commerce”, like it or not.
History: Sacred and Secular
The bitterness of post-Theodosian fourth-century theological polemics did not affect historiography, as pagan and Christian historiographers (such as Ammianus Marcellinus and Orosius of Braga, respectively) “had almost entirely different interests, and there could be no conflict between them because their concerns met at scarcely any point.”  The question could not be ignored: how did the events upon which the Christian faith rests fit into general world history? The answer: world history was to be mapped “with the aid of the fixed points in the story of redemption.” Universal history might then “be read as bound up with man’s destiny.”
Yet after A.D. 410 Augustine recognized the “need for a new kind of Christian historical apologetic.” Before this, Augustine’s “attitudes” towards history were “like those of most fourth-century Christians.”  The DDC is where Augustine “came most closely to grips with the place that history ought to occupy in the Christian curriculum of studies.” No longer, for the DDC, was history organized by the scriptural patterns into one overarching sacred history: history was permitted only to the extent that it might aid in understanding the scriptures. Augustine’s “interest in extra-biblical history […] had  arisen from the need to think of world history as including the biblical history, and it remained confined within this perspective.” Augustine had taken over the standard “distinction between the biblical redemption history and all other history” and sought the grounds for this distinction.
The distinction may be thought of as somewhat gradual, so that pagan history –and especially pagan philosophy– is regarded as a “preparation for the Gospel” (praeparatio evangelica), leading seamlessly into the narratives of the Gospels. Still, there is a gulf, for the Gospel treats contingent events about Jesus, and philosophy proceeds according to “abstract, general method[s] of argumentation” that cannot reach the contingent, historical truths of the Gospels.  So the biblical text is regarded as a “privileged strand of history” . Markus thus employs the terms “sacred history” and “secular history” to describe this distinction, though Augustine didn’t use these terms. “[W]e may define sacred history as the story of God’s saving work, secular history as all […] that is left […] when we subtract from history the strand singled out as ‘sacred’.”  Sacred and secular history both “arise from [the] primal tragedy” of Adam’s fall. “Temporality itself is involved in being created; but temporality falls short of historicity. Historicity is the mark of a world in which there is nihil solidum, nihil stabile.” 
All events are from God, Augustine writes, and God can “speak not only with words but also with events”, but not all events “speak” — at least, not the same way.  What distinguishes some events as carrying “a distinctive divine voice?” Augustine simply assumes divine inspiration without working out a theory of it; yet he does make “remarks on the nature of prophetic insight”  involving “perception, imagination, and judgment.” Prophecy is not merely visionary activity or “perception of what is hidden,” for “[i]nsight into the meaning of public events” and “a special quality of judgment or of understanding” are central. This prophetic insight accounts for the distinction between sacred and secular history,  since history is not made up of events, but of statements about events; sacred history has this “special quality attached” of prophecy. “The privileged status of sacred history derives from the privileged status of the biblical authors and hence of their stories, rather than from the nature of the events they tell of.”  The selection and omission of events in the telling are part of prophetic judgment.
Augustine “abandon[ed] this way of speaking” by the time he wrote the CoG; by then, “[s]acred history is simply what is found in the scriptural canon.”  ‘Secular’ history becomes simply “extrabiblical” history, even when it casts “light directly on the economy of salvation”. In a sense, all events might be said to sing the divine symphony, but “only ‘sacred history’ tells us” what the song is, and what the melody of those events in secular history is.  In short: “[t]he meaning and structure of history derive from sacred history.” 
Augustine followed the patristic “commonplace”  of dividing history into seven ages, “foreshadowed” by the seven-day creation story. Christ inaugurates the sixth age, which ends with his return. This “periodisation is brought into relation with another scheme: a map of human history drawn on the analogy of man’s progress from infancy through childhood, adolescence, manhood and senescence to death.”  Both models are Christian and pagan commonplaces. Yet Christians introduced the “theme of rejuvenation in that last age”, which eclipsed the sevenfold model and “reduced the previous five ages to one.” Augustine describes this effectively twofold division as falling into promise (on the one hand) and fulfillment (on the other).
Some Christian writers, continuing to use the seven-ages-and-seven-days model, took Psalm 90:4, “with the Lord, a thousand years is as a day”, to indicate that these ages would last 1,000 years each; Augustine “goes out of his way to dissociate himself with [this] idea”  and to “repudiate”  the often-associated “naïve millenaristic speculations” that “were again being dreamt” near the turn of the century. Against this trend Augustine “display[ed] one of the fundamental themes of his reflection on history: that since the coming of Christ, until the end of the world, all  history is homogenous, that it cannot be mapped out in terms of a pattern drawn from sacred history”.
Every moment may have its unique and mysterious significance in the ultimate tableau of men’s doings and sufferings; but it is a significance to which God’s revelation does not supply the clues. 
All history after sacred history (until the end of history) is, thus, secular history.