'Abba, for the hundredth time, you need to keep adequate security on you at all times." Just one week ago, I sleepily voiced my concern for my father's security at our 8am family breakfast.

As usual, he brushed aside my unease at the escalating threats he had been receiving. Summoning a small smile, he kissed his Ayat-ul-kursi (protective verses from the Koran) hanging around his neck and quoted the great historian Thomas Babington Macaulay: "How can a man die better than facing fearful odds for the ashes of his fathers and the Temple of his Gods?"

And, a few days later, on my 25th birthday, that is how my father died. He was gunned down in cold blood by a man who veiled his inhumane deed in a perverse ideology of Islam. He thereby blackened the name of Islam, and of our country, Pakistan.

It was his outspoken support for the minorities and the oppressed that led to my father's assassination. Salmaan Taseer was the most prominent advocate pushing for amending an extremist Blasphemy Law inserted by the dictator General Mohammad Zia ul-Haq in the Constitution of Pakistan in 1977.

That law is the reason that Aasia Bibi now languishes in prison, in solitary confinement and in fear for her life; my father's fight against it so enraged some people in my country that they have found themselves unable to pay their respects even in death, suggesting that he deserved no better a fate. Some of those exulting in the crime even threw rose petals to celebrate the man who is said to be his assassin.

But had he known of all this, none of it would have changed my father's determination to fight for his cause. He always told me that a man's mettle is determined not by how many strong shoulders he leans on, but by how many weak hands he holds. I believe that we must continue to support the oppressed, and not succumb to the fear spread by terrorism.

My father wanted his children to live in a Pakistan envisioned by Muhammad Ali Jinnah [the country's founder] – a liberal Pakistan, a tolerant Pakistan. He said that without liberation there is no tolerance; he believed in problem solving through reasoning and dialogue, a true democrat's approach. At his inauguration as Governor, he stated that "from this day on, all the doors of the Governor's House are open to the public." He welcomed open discussion and debate.

He attempted to bolster his democratic ideal by vigorously promoting education. In his role as Governor, and therefore Chancellor of all the universities and schools of Punjab, he attended every convocation during his incumbency.

As the Guest of Honour, he gave motivational speeches, urging the youth to continue their education and to give back to a country that has given them so much. At my younger sister's graduation in 2006, he spoke of how important it was to revere the ustaad – an honorific title for teachers and artists. He highlighted that the ustaad is the ultimate mentor – like the North Star – a beacon of light, a guide through darkness.

Like his father before him, he enthusiastically promoted the arts, culture and sport. From poetry, sufi and Koranic recitals at the Governors house, exhibitions at the National College of Arts, to the sports day at the Lawrence College where I accompanied him. I distinctly remember the number of times that a serious conversation about politics or literature was interrupted by his enthusiastic "Yes" in reaction to a wicket taken by Pakistan on a muted television. He loved his cricket as much as any of his countrymen, and flew around the world to cheer the Pakistani team on.

He came from humble beginnings: he was a self-made man, who recovered from even the adversity of losing a fortune to make another one. He used the many opportunities and resources in Pakistan to climb to remarkable entrepreneurial and political success. Tortured for his beliefs in democracy under Gen Zia ul-Haq's regime, he nevertheless retained his firm belief that our country has enough potential to strive towards the self-sustenance that it so desperately needs.

My entire childhood, I idolised my father: he was my hero. He was an expert journalist, accountant, business man, entrepreneur, politician and a humanist. As an avid reader, he was well informed on the lives and doings of many of history's great men, and often quoted from their memoirs.

His magnitude to me cannot be described, except in the most meagre terms, because any valuation, even as his son, remains subjective. For my father, it always seemed to me, the world was an infinite playground. With all that he achieved, I always compared his success with that of Alexander the Great – when Alexander looked upon his domains, he wept, for there were no more worlds left to conquer.

Now my father is gone. But weep as we might, we – his family and friends, and the many people who share his profound beliefs – also know that his values, the significant work of his life, have not been conquered, and never can be.

At times in life we must lose something before we recognise its worth. This is not the case with my father. To me, my father exemplified all the values of a great man during his lifetime. He used to say that all his father had left him was his name and some books; I can safely say my father has left me with so much more – a legacy to live up to, and to take forward.

An extraordinary family

* Salmaan Taseer came from a prominent literary and left-wing family, and later built up a business empire with interests in banking, chartered accountancy and the media.

Taseer's father, Dr MD Taseer, was a well-known progressive poet. He married Christabel George, an Englishwoman who had travelled with her sister to India in the Thirties to support the struggle for independence against the British. Christabel's sister, Alys, married an even more famous poet, Faiz Ahmed Faiz. After losing his father early in his childhood, Taseer claimed Faiz as a mentor, going on to live with him in London during his exile years.

Taseer's businesses included a liberal English language daily, 'The Daily Times', and a business channel, 'Business Plus'. His son, Shehryar Taseer, the author of this piece and one of seven children, runs the media company. His sister-in-law, Ayesha Tammy Haq, the noted Pakistani columnist, hosts a political talk show on Business Plus.