J. Douglas MacMillan was a Christian

Christian

A Christian is a person who adheres to Christianity, an Abrahamic, monotheistic religion based on the life and teachings of Jesus of Nazareth as recorded in the Canonical gospels and the letters of the New Testament...

 minister in the Free Church of Scotland

Free Church of Scotland (post 1900)

Free Church of Scotland is that part of the original Free Church of Scotland that remained outside of the union with the United Presbyterian Church of Scotland in 1900...

. MacMillan was born the youngest of six children, on the Ardnamurchan

Ardnamurchan

Ardnamurchan is a peninsula in Lochaber, Highland, Scotland, noted for being very unspoilt and undisturbed. Its remoteness is accentuated by the main access route being a single track road for much of its length.-Geography:...

 peninsula in Argyll

Argyll

Argyll , archaically Argyle , is a region of western Scotland corresponding with most of the part of ancient Dál Riata that was located on the island of Great Britain, and in a historical context can be used to mean the entire western coast between the Mull of Kintyre and Cape Wrath...

. He was converted at the age of 21, and studied at the University of Aberdeen

University of Aberdeen

The University of Aberdeen, an ancient university founded in 1495, in Aberdeen, Scotland, is a British university. It is the third oldest university in Scotland, and the fifth oldest in the United Kingdom and wider English-speaking world...

 and at the Free Church College. After his ordination, he ministered at St. Columba in Aberdeen (1966–1974) and St Vincent Street in Glasgow (1974–1982), before taking up an appointment as Professor of Church History at the Free Church College

Free Church College

The Free Church College is a theological seminary in Edinburgh connected to the Free Church of Scotland. It traces its origins back to the foundation of New College, Edinburgh at the time of the Disruption of 1843...

. Since 1994, the biennial MacMillan Lecture in Evangelism has been held at that institution in his honour.

According to Hywel Jones, MacMillan's preaching was marked by "powerful originality and strong orthodoxy". He is best known for his book The Lord Our Shepherd (ISBN 1850491984). This is an exposition of Psalm 23

Psalm 23

In the 23rd Psalm in the Hebrew Bible/Old Testament, the writer describes God as his Shepherd. The text, beloved by Jews and Christians alike, is often alluded to in popular media and has been set to music....

, originally given to the Evangelical Movement of Wales

Evangelical Movement of Wales

The Evangelical Movement of Wales was born in the 1940s, it came to light as a counter move by reformed Christians to the liberal theology which was gaining influence in to the Protestant denominations of Wales during the 20th century....

 in 1979. MacMillan drew on his 12 years of experience as a shepherd on the to argue that the shepherd theme pervades the entire psalm.

MacMillan wrote a number of other books including Wrestling with God (ISBN 1850490740) consisting of addresses on the life of Jacob

Jacob

Jacob "heel" or "leg-puller"), also later known as Israel , as described in the Hebrew Bible, the Talmud, the New Testament and the Qur'an was the third patriarch of the Hebrew people with whom God made a covenant, and ancestor of the tribes of Israel, which were named after his descendants.In the...

 given to the Evangelical Movement of Wales

Evangelical Movement of Wales

The Evangelical Movement of Wales was born in the 1940s, it came to light as a counter move by reformed Christians to the liberal theology which was gaining influence in to the Protestant denominations of Wales during the 20th century....

in 1983, Jesus: Power Without Measure (ISBN 1850490910), Restoration in the Church (ISBN 1871676029) and The God of All Grace (ISBN 1857922409).

MacMillan had five children with his wife, Mary.