Tilak was one of the first and strongest advocates of Swaraj ("self-rule") and a strong radical in Indian consciousness. He is known for his quote in Marathi: "Swarajya is my birthright and I shall have it!". He formed a close alliance with many Indian National Congress leaders including Bipin Chandra Pal, Lala Lajpat Rai, Aurobindo Ghose, V. O. Chidambaram Pillai and Muhammad Ali Jinnah.
He obtained his Bachelor of Arts in first class in Mathematics from Deccan College of Pune in 1877. He left his M.A. course of study midway to join the L.L.B course instead, and in 1879 he obtained his L.L.B degree from Government Law College. After graduating, Tilak started teaching mathematics at a private school in Pune. Later, due to ideological differences with the colleagues in the new school, he withdrew and became a journalist. Tilak actively participated in public affairs. He stated: "Religion and practical life are not different. The real spirit is to make the country your family instead of working only for your own. The step beyond is to serve humanity and the next step is to serve God."
Inspired by Vishnushastri Chiplunkar, he co-founded the New English school for secondary education in 1880 with a few of his college friends, including Gopal Ganesh Agarkar, Mahadev Ballal Namjoshi and Vishnushastri Chiplunkar. Their goal was to improve the quality of education for India's youth. The success of the school led them to set up the Deccan Education Society in 1884 to create a new system of education that taught young Indians nationalist ideas through an emphasis on Indian culture. The Society established the Fergusson College in 1885 for post-secondary studies. Tilak taught mathematics at Fergusson College. In 1890, Tilak left the Deccan Education Society for more openly political work. He began a mass movement towards independence by an emphasis on a religious and cultural revival.
Tilak had a long political career agitating for Indian autonomy from British colonial rule. Before Gandhi, he was the most widely known Indian political leader. Unlike his fellow Maharashtrian contemporary, Gokhale, Tilak was considered a radical Nationalist but a Social conservative. He was imprisoned on a number of occasions that included a long stint at Mandalay. At one stage in his political life he was called "the father of Indian unrest" by British author Sir Valentine Chirol.
During late 1896, a bubonic plague spread from Bombay to Pune, and by January 1897, it reached epidemic proportions. The British Indian Army was brought in to deal with the emergency and strict measures were employed to curb the plague, including the allowance of forced entry into private houses, the examination of the house's occupants, evacuation to hospitals and quarantine camps, removing and destroying personal possessions, and preventing patients from entering or leaving the city. By the end of May, the epidemic was under control. The measures used to curb the pandemic caused widespread resentment among the Indian public. Tilak took up this issue by publishing inflammatory articles in his paper Kesari (Kesari was written in Marathi, and "Maratha" was written in English), quoting the Hindu scripture, the Bhagavad Gita, to say that no blame could be attached to anyone who killed an oppressor without any thought of reward. Following this, on 22 June 1897, Commissioner Rand and another British officer, Lt. Ayerst were shot and killed by the Chapekar brothers and their other associates. According to Barbara and Thomas R. Metcalf, Tilak "almost surely concealed the identities of the perpetrators". Tilak was charged with incitement to murder and sentenced to 18 months imprisonment. When he emerged from prison in present-day Mumbai, he was revered as a martyr and a national hero. He adopted a new slogan coined by his associate Kaka Baptista: "Swaraj (self-rule) is my birthright and I shall have it."
Following the Partition of Bengal, which was a strategy set out by Lord Curzon to weaken the nationalist movement, Tilak encouraged the Swadeshi movement and the Boycott movement. The movement consisted of the boycott of foreign goods and also the social boycott of any Indian who used foreign goods. The Swadeshi movement consisted of the usage of natively produced goods. Once foreign goods were boycotted, there was a gap which had to be filled by the production of those goods in India itself. Tilak said that the Swadeshi and Boycott movements are two sides of the same coin.
Tilak opposed the moderate views of Gopal Krishna Gokhale, and was supported by fellow Indian nationalists Bipin Chandra Pal in Bengal and Lala Lajpat Rai in Punjab. They were referred to as the "Lal-Bal-Pal triumvirate". In 1907, the annual session of the Congress Party was held at Surat, Gujarat. Trouble broke out over the selection of the new president of the Congress between the moderate and the radical sections of the party. The party split into the radicals faction, led by Tilak, Pal and Lajpat Rai, and the moderate faction. Nationalists like Aurobindo Ghose, V. O. Chidambaram Pillai were Tilak supporters.
When asked in Calcutta whether he envisioned a Maratha-type of government for independent India, Tilak answered that the Maratha-dominated governments of 17th and 18th centuries were outmoded in the 20th century, and he wanted a genuine federal system for Free India where everyone was an equal partner. He added that only such a form of government would be able to safeguard India's freedom. He was the first Congress leader to suggest that Hindi written in the Devanagari script be accepted as the sole national language of India.
During his lifetime among other political cases, Tilak had been tried for sedition charges in three times by British India Government—in 1897, 1909, and 1916. In 1897, Tilak was sentenced to 18 months in prison for preaching disaffection against the Raj. In 1909, he was again charged with sedition and intensifying racial animosity between Indians and the British. The Bombay lawyer Muhammad Ali Jinnah appeared in Tilak's defense but he was sentenced to six years in prison in Burma in a controversial judgement. In 1916 when for the third time Tilak was charged for sedition over his lectures on self-rule, Jinnah again was his lawyer and this time led him to acquittal in the case.
On 30 April 1908, two Bengali youths, Prafulla Chaki and Khudiram Bose, threw a bomb on a carriage at Muzzafarpur, to kill the Chief Presidency Magistrate Douglas Kingsford of Calcutta fame, but erroneously killed two women traveling in it. While Chaki committed suicide when caught, Bose was hanged. Tilak, in his paper Kesari, defended the revolutionaries and called for immediate Swaraj or self-rule.
The Government swiftly charged him with sedition. At the conclusion of the trial, a special jury convicted him by 7:2 majority. The judge, Dinshaw D. Davar gave him a six years jail sentence to be served in Mandalay, Burma and a fine of ₹1,000 (US$14). On being asked by the judge whether he had anything to say, Tilak said: "All that I wish to say is that, in spite of the verdict of the jury, I still maintain that I am innocent. There are higher powers that rule the destinies of men and nations; and I think, it may be the will of Providence that the cause I represent may be benefited more by my suffering than by my pen and tongue."
Muhammad Ali Jinnah was his lawyer in the case. Justice Davar's judgement came under stern criticism in press and was seen against impartiality of British justice system. Justice Davar himself previously had appeared for Tilak in his first sedition case in 1897. In passing sentence, the judge indulged in some scathing strictures against Tilak's conduct. He threw off the judicial restraint which, to some extent, was observable in his charge to the jury. He condemned the articles as "seething with sedition", as preaching violence, speaking of murders with approval. "You hail the advent of the bomb in India as if something had come to India for its good. I say, such journalism is a curse to the country". Tilak was sent to Mandalay from 1908 to 1914. While imprisoned, he continued to read and write, further developing his ideas on the Indian nationalist movement. While in the prison he wrote the Gita Rahasya. Many copies of which were sold, and the money was donated for the Indian Independence movement.
Tilak developed diabetes during his sentence in Mandalay prison. This and the general ordeal of prison life had mellowed him at his release on 16 June 1914. When World War I started in August of that year, Tilak cabled the King-Emperor George V of his support and turned his oratory to find new recruits for war efforts. He welcomed The Indian Councils Act, popularly known as Minto-Morley Reforms, which had been passed by British Parliament in May 1909, terming it as "a marked increase of confidence between the Rulers and the Ruled". It was his conviction that acts of violence actually diminished, rather than hastening, the pace of political reforms. He was eager for reconciliation with Congress and had abandoned his demand for direct action and settled for agitations "strictly by constitutional means" – a line that had long been advocated by his rival Gokhale.[additional citation(s) needed] Tilak reunited with his fellow nationalists and rejoined the Indian National Congress during the Lucknow pact 1916.
Tilak tried to convince Mohandas Gandhi to leave the idea of Total non-violence ("Total Ahimsa") and try to get self-rule ("Swarajya") by all means. Though Gandhi did not entirely concur with Tilak on the means to achieve self-rule and was steadfast in his advocacy of satyagraha, he appreciated Tilak's services to the country and his courage of conviction. After Tilak lost a civil suit against Valentine Chirol and incurred pecuniary loss, Gandhi even called upon Indians to contribute to the Tilak Purse Fund started with the objective of defraying the expenses incurred by Tilak.