He was a keen member of the university's debating club and other societies promoting radical thought, including spiritualism. The sixteen-year-old was also the editor of a spiritualist paper. When he became a barrister in 1878, he had already written a play (Quentin Massys) and published a long book, A New Pilgrim's Progress. His law career was slow to grow and for several years he earned money writing for a leading Melbourne newspaper, The Age. The Editor of the paper Mr David Syme was influential in the development of his protégé's ideas, prompting him to change from a belief in free trade to become a protectionist. He also helped him to win the rural seat of West Bourke in the Victorian parliament in 1879. Deakin resigned in his maiden speech on 8 July 1879, claiming irregularity in the poll.
He lost the subsequent by-election, but was re-elected in July 1880 and held the seat for ten years. He became Commissioner for Public Works and Water Supply in 1883, and Solicitor-General and Minister of Public Works the following year. In 1885 Deakin secured the passage of the colony's pioneering Factories and Shops Act, enforcing regulation of employment conditions and hours of work.
In 1887 Deakin led Victoria's delegation to the Imperial Conference in London. He was a young colonial politician who made a strong impact arguing forcibly for more favourable terms in the colonial naval agreement. With Queensland's delegate, Samuel Griffith, he confronted the British Prime Minister, Lord Salisbury, on colonial interest in the New Hebrides.
After the fall of the government in October 1890, Deakin remained a backbencher throughout the 1890s. Like many others, Deakin lost heavily in the 1893 financial collapse and had to practice law to supplement his salary and repay his debts. His frustration that the competitive divisions between the colonies prevented a united front at the 1887 Imperial Conference fuelled his support for Federation throughout the 1890s.
In 1890 Deakin was Victoria's delegate to the Australasian Federal Conference, held in Melbourne, which agreed to hold an intercolonial convention to draft a federal constitution. The following year, Deakin was the colony's delegate to this meeting, the first National Australasian Convention held in Sydney, which produced a draft Constitution Bill.
Deakin became Victoria's most prominent federationist. His splendid oratory enlivened meetings throughout Victoria, from the annual conference of the Australian Natives Association in 1893, to the public meetings leading up to the Federation referendum in June 1898.
Deakin was founding chairman of the Federal League of Victoria in 1894, and attended the Federal Council meeting in Hobart in 1896. In 1897 he was a delegate to the second Australasian Federal Convention, which opened in Adelaide in March 1897 and concluded in Melbourne in January 1898.
Deakin and the Victorian Premier, George Turner, ensured the Constitution Bill passed the Victorian parliament and could be put to the colony's voters at an 1898 referendum. South Australia, Tasmania and Victoria were the first colonies to pass Federation referendums. Between April and September 1899, successful referendums were held in all colonies, except Western Australia, enabling the Bill to be submitted to the British parliament.
In 1900, Deakin was a member of the delegation led by Edmund Barton to lobby in London for the successful passage of the Australian Constitution Bill through the British parliament. The joy of the delegates when the Bill was passed in June, was exceeded only by the triumph in every colony when the news was received that it had become law with Queen Victoria's assent on 9 July 1900.
After the first federal elections in March 1901, Deakin served as leader of the House as well as Attorney-General. He had a heavy workload throughout the first parliament, with its mass of machinery bills as well as policy legislation on immigration. Robert Garran took major responsibility for drafting legislation, though Deakin himself was substantially responsible for the Public Service and Conciliation and Arbitration bills.
With the support of Edmund Barton and Isaac Isaacs, Deakin argued forcefully against delaying the establishment of the High Court. He viewed the Court as the essential third pillar of the federal structure once the parliament and public service were in place. The Bill was not passed until September 1903 and, in a compromise with budget-wary opponents, the High Court bench was reduced from five to three judges.
In 1902 Deakin served as Acting Prime Minister from May to September, while Edmund Barton was overseas for the coronation of King Edward VII and Queen Alexandra. Atlee Hunt, a Sydney protégé of Barton and Secretary of the Department of External Affairs, took a leading role in dealing with the prime ministerial business. During Barton's absence, Hunt and Deakin developed the working relationship that extended over the next decade, during Deakin's three terms as Prime Minister between 1903 and 1910.
This controversial measure had its first casualty with the resignation of Charles Kingston over a Cabinet amendment to exclude seamen on coastal ships. This Bill was also instrumental in bringing down two governments and splitting Deakin's Protectionist supporters, before agreement was finally hammered out. The statute was finally enacted in December 1904.
Deakin served as Prime Minister and Minister for External Affairs from 24 September 1903 to 27 April 1904 and from 5 July 1905 to 13 November 1908. He was again Prime Minister - this time leading a Fusion government that comprised the non-Labor parties - from 2 June 1909 to 29 April 1910. In July 1903 Deakin took over the conduct of a second bill vital to implementing a provision of the Constitution, the Conciliation and Arbitration Bill.
Deakin's government was instrumental in establishing and strengthening the essential machinery of state. His second term (1905-08) was his most significant, earning him the title 'the constructor' as his government dealt with issues including the public service, defence policy and military infrastructure, external affairs, federal financial relations and the High Court. Other important measures included the transfer of the Northern Territory from South Australia to the Commonwealth, establishing Canberra as the federal capital site and amendments to the Judiciary Act and the Immigration Restriction Act.
Deakin's second term, like his first, depended upon Labor Party support, and his government was defeated when disagreements over legislation prompted Labor to withdraw from the alliance. Deakin's total period in office amounted to four years and ten months, the longest time served by any of the six Prime Ministers to 1915.
Despite relatively short and discontinuous periods in office, his governments were responsible for much policy and legislation giving shape to the Commonwealth during its first decade. Among the achievements during Deakin's periods as Prime Minister were:
Deakin remained Leader of the Opposition (and of the Liberal Party he founded in 1909) until ill health forced his resignation in January 1913. He retired from politics when the fourth parliament expired on May 1913.
He participated little in public life after his retirement, though he did chair the 1914 Royal Commission on Food Supplies and on Trade and Industry During the War and was the Commonwealth's official representative at the Panama exhibition in 1915.
After suffering increasing ill-health and progressive memory loss during his retirement, Deakin died from a stroke on 7 October 1919.
Deakin was given a state funeral, his coffin brought from his house in Walsh Street, South Yarra to Parliament House. It was taken from there in a silent procession through the city streets. He was buried in the St Kilda cemetery next to the graves of his parents.