It is impossible to read Heroism and Genius: How Catholic Priests Helped Build – and Can Help Rebuild – Western Civilization by William J Slattery (Ignatius), without being caught up by the author’s enthusiasm for his subject, alongside his evident knowledge and erudition. Starting in AD 200 he goes through the centuries, showing how priests (including bishops, saints and theologians) painstakingly brought a Christian culture to bear on the Dark Ages. As Lord Clark was to demonstrate in his television series, Civilisation, Slattery explains how a Catholic civilization, long-germinating, came to birth by the 11th century in law, philosophy, art and architecture.

The author, ordained to the priesthood by John Paul II in St Peter’s in 1991, is clearly in love with his vocation. His book, beautifully illustrated, is an imaginative and scholarly reflection on a comment of Benedict XVI: “If we look at history we can see that many episodes of authentic spiritual and social renewal have been written with the decisive contribution of Catholic priests.”

Slattery’s book has an urgent purpose; it is a rallying call to priests today as they “confront the Western civilization of the past and the dictatorship of relativism of the present.” Its author takes a sombre view of the Western world today, describing it as being “like that of the Dark Ages…one of cultural turmoil, one in which men and women live atomistic existences amid increasingly soulless megacities.” Yet despite the priest abuse scandals, a fall in vocations, the closing of hundreds of parishes and widespread lapsing among young people, Slattery has an unswerving vision of hope.

I asked him what had inspired him to write it. He responds instantly: “Urgency! It’s time for us Catholics to do again what we did during the first “Dark Ages” – to begin “the long march through the institutions” in order to recapture them and build a new Christian civilization.” To do this he believes that we “must form everywhere creative Catholic minorities, including the training of future leaders to act with the insight that springs from a historical imagination.”

Slattery reflects that as he worked on his book in the 17th-century library of the Pontifical North American College near the ancient Forum in Rome, “I wanted to empower young Catholics with this “historical imagination”. Another motivation “was the hope that the spirit that imbued the builders of Christendom would also inspire the first members of a new order of priests, the Society of Ignatians” whose foundation, he tells me, will take place in the US on 31 July 2018.

Buoyed up with the same urgency and historical imagination that resulted in his book, the author emphasises to me that his main purpose in writing it was “to shout that Catholicism matters – not just to the individual soul but to society’s soul.” He is convinced that only a renewed Catholic civilisation “has the intellectual clarity and supernatural guts to overcome our cultural Marxism.”

Slattery sees his book as a summons to contemporary Catholics “to remember as you stand at a crossroads of history who you are and what you once achieved. Become familiar with the awe-inspiring story of how Catholics laid the foundations of all that is true, good and beautiful in western civilisation during an age of great darkness, so that present-day priests and laity may once again become active in their missionary and evangelical mandate.”

Slattery provides a heroic roll-call in his book of the great personalities that dominated the Church and society in the past. Does he have a particular favourite? He starts to describe St Ambrose of Milan, a man who combined authority with pastoral and aesthetic sensitivity, then gets carried away, recalling St Augustine of Hippo; Leo the Great – “who rode out on horseback to save Rome from Attila the Hun”; Gregory the Great – “forcing his weary body to plan the conversion of England”; Abbot Suger, founder of Gothic architecture; Alcuin , “mentor of Charlemagne” – as well as all the “quiet, unsung heroes of the priesthood, such as the Irish priests during the Famine of 1845 who were described by government officials as “labouring like tigers…working day and night.”

But does the author seriously think that the decline of the faith in the west can be reversed? Again, Slattery answers unhesitatingly: “What we did before, we can do again.” He does not shirk mentioning the corruption of the papacy and how “barbarianism abounded, even inside the ranks of churchmen” but then refers me to the rebirth of Christian culture in the 12th century, with the building of the great Gothic cathedrals, the ideals of chivalry changing “men with claws” into Christian knights, a “sublime romanticism idealising women” and so on.

He tells me, “All we have to decide is what to do with the time that is given us.” At the parish level he suggests the laity must be strong in their Catholic identity: support the traditional Latin Mass where possible, because “Catholic tradition is the core identity of Catholicism”; join fellow Catholics in pro-life societies; go on pilgrimages to Walsingham or Chartres; work through the Catholic social media; and educate young people through integrally Catholic schools or even home-schooling.

Finally I ask him what sort of formation seminarians should have, given the formidable challenges they will face as priests. He quotes Herald journalist Tim Stanley, a convert, who once said, “I can’t count the number of times I’ve sat with Catholic priests, listened to them talk softly about the problems of the world and wanted to scream: “What do you believe, man?! Identify it, testify it and let’s save some souls!”

Summarising, Slattery is clear that priests need to have “a Catholic and priestly identity and to be creators of creative minorities.” They need to be equipped in five key areas: in celebrating the liturgy; in theology; as pro-convert missionaries; as persuasive communicators for the “contemporary mass-media mentality”; and “by acquiring an historical imagination, because to re-build we must remember: remember who you are and that by being truly Catholic you will change society; you simply cannot fail.”