In God they trust?

Since Federation, excluding "stop gap" appointees, Australia has had 23 prime ministers. Almost all of them thought long and hard about God. In general, they were much more spiritually-minded than the people they led.

I have come to agree wholeheartedly with an observation of the late Kim Beazley Senior: "In our secular age, biographers rarely give a person's spiritual life the attention it deserves".

If we accept that religious feeling is a key determinant of personal behaviour, it follows that anyone interested in Australian history or public policy ought to know what our leaders believed about God, particularly during their terms in office. The record shows that their decision-making was often affected by their faith, and not merely as regards matters patently "moral" or "spiritual". It extended to the perennial issues of practical politics: the distribution of wealth, wars and national participation in them, and the recognition and enforcement of human rights.

Of course, a degree of caution must be exercised. It is hazardous to be dogmatic about the content and sincerity of anyone else's faith. Ultimately, faith is a personal thing: only you know for sure what is in your heart, and only God sees our every step (Job 34:21). But, for an outsider, I suggest a few useful rules of thumb. Actions – church-going, Bible-reading, evangelism, charitable works, peace-making, humility, piety, kindness – speak louder than words. And words written or spoken in private are more likely to be reliable than those for public consumption.

How many of our 23 prime ministers were believers in God? By that I mean believers in God as at the time of their death, or, in the case of the still-living prime ministers, as at the present day. My own count is sixteen believers to seven unbelievers. There may be room for argument about a few, but even the clear-cut unbelievers have a fascinating "religious" story to tell. Harold Holt's is the only open-and-shut case of lifelong agnosticism.

Our prime ministers can be grouped into eight broad categories. To some extent these are artificial, but they serve to highlight the various religious "types" who have directed the nation's affairs since Federation.

The good and faithful servants

• Andrew Fisher (Labor: 1908-09, 1910-13, 1914-15)
• James Scullin (Labor: 1929-31)
• Joseph Lyons (United Australia Party: 1932-39)

Each of these thoroughly admirable men was born into the Christian faith and married a woman from the same denomination. None were theologians of any note, but each adhered assiduously to his church's tenets – or sought to. Only one of them, Fisher, was a Protestant. Scullin and Lyons were Catholics, and, at the height of the Great Depression, they fought the December 1931 election. In retrospect, that election can be seen as marking the beginning of the long and tortuous process whereby religious sectarianism was (more or less) eradicated from Australian society. Fittingly, and not coincidentally, Joseph Lyons was a key figure. His wife Enid (nee Burrell) converted from Methodism to Catholicism prior to their marriage. On May 8, 1938, both Lyons and Scullin attended the laying of the foundation stone of the new St Christopher's Catholic Church in Canberra, where they both became parishioners.

The ardent seekers

• Alfred Deakin (Protectionist: 1903-04, 1905-08; Commonwealth Liberal: 1909-10)
• William (Billy) McMahon (Liberal: 1971-72)
• Kevin Rudd (Labor: 2007-10, 2013-)

All three of these men were university-educated and spoke and wrote extensively about their faith. Each of their spiritual journeys was different, but they had one major trait in common: a genuine passion for theology. Deakin was the most prolific author and the most unorthodox in his beliefs. He was an exceptionally intelligent and well-read man. So is Rudd. McMahon, though not in their league, should not be underestimated in either capacity. Both Rudd and McMahon moved from Catholicism to Anglicanism, and were accused by their opponents – within and outside their own parties, of using "religion" for political advantage. In my judgment the charge was (is) largely unfair in both cases.