Theoretical physicist and science communicator Stephen Hawking was one of the smartest and most vocal scientists in the world, but he was also one of the most political.
Never one to shy away from a controversial issue, Hawking used his analytical mind and wealth of knowledge to weigh in on some of the most hotly debated political issues of his time.
After all, Hawking knew there was a difference between allowing politics to influence science and allowing science to influence politics.
Far from being a partisan voice, when it came to issues like climate change, overpopulation, nuclear war or artificial intelligence, Hawking was a scientific beacon.
Wherever science intersected with politics, there was Hawking, forever unafraid to use his expertise and sophisticated viewpoint to enlighten, advise and warn.
Now that he is gone, we need other scientists to step up and fill the void that his expertise has left behind.
Before the Brexit vote, Hawking warned that leaving the European Union would seriously damage scientific research in Britain.
"British science needs all the money it can get, and one important source of such funding has for many years been the European commission," he wrote in a piece for The Guardian.
"Without these grants, much important work would not and could not have happened."
In his article, he warned that unless humanity sheds themselves of "envy" and "isolationism", he does not have much hope for the future of our species.
After the UK voted to leave the EU, Hawking said he was "sad about the result."
But Hawking could always find the humor - even in the most difficult situations.
While receiving an award from Prime Minister Theresa May, he joked, "I deal with tough mathematical questions every day, but please don't ask me to help with Brexit."
The room erupted in laughter.
2. The US withdrawal from the Paris Climate Accord
When President Trump withdrew the US from the Paris Climate Accord, Hawking condemned the decision in the strongest words.
"Climate change is one of the great dangers we face and it's one we can prevent if we act now," he told the BBC.
"By denying the evidence for climate change and pulling out of the Paris Climate Agreement, Donald Trump will cause avoidable environmental damage to our beautiful planet, endangering the natural world, for us and our children."
In his time, Hawking was a vocal climate activist, and he often spoke out against those who dened the reality of human-caused climate change. The President of the United States was no exception.
"Unlike Donald Trump, who may just have taken the most serious and wrong decision on climate this world has seen, I am arguing for the future of humanity and a long-term strategy to achieve this," Professor Hawking said in a Skype talk delivered at the Starmus science and arts festival.
3. Robots and Capitalism
In a 2015 Reddit AMA, Hawking was asked what he thought about the possibility of technological unemployment in an age of artificial intelligence.
In his response, Hawking said he believed there was nothing wrong with robots taking more work, as long as the wealth generated from that work was evenly distributed.
"If machines produce everything we need, the outcome will depend on how things are distributed," he replied.
"Everyone can enjoy a life of luxurious leisure if the machine-produced wealth is shared, or most people can end up miserably poor if the machine-owners successfully lobby against wealth redistribution."
"So far," he added, "the trend seems to be toward the second option, with technology driving ever-increasing inequality."
In the short term, it appears as though Hawking was more afraid of unchecked capitalism than he was of AI. In the long term, however, Hawking was afraid that AI would replace humans altogether.
"If people design computer viruses, someone will design AI that improves and replicates itself. This will be a new form of life that outperforms humans," he said in an interview with Wired magazine.
As a solution, Hawking said he thought we needed a 'world government' to regulate the development of AI.
4. Nuclear war
Hawking was an active proponent of worldwide nuclear disarmament. In a speech at Oxford University Union, Hawking predicted that humanity only had about 1,000 years left of viable existence on planet Earth.
"The human failing I would most like to correct is aggression. It may have had survival advantage in caveman days, to get more food, territory or a partner with whom to reproduce, but now it threatens to destroy us all," Hawking told The Independent.
"A major nuclear war would be the end of civilization, and maybe the end of the human race."
Never one to sit back and complain, in 2007, Hawking fronted a campaign by scientists, Church leaders, actors and writers, urging then Prime Minister Tony Blair to cancel the UK's nuclear programme Trident.
"Nuclear war remains the greatest danger to the survival of the human race," he said at the time.
"To replace Trident would make it more difficult to get arms reduction, and increase the risk. It would also be a complete waste of money because there are no circumstances in which we would use it independently."
He continued to lead similar campaigns against the Trident program for the rest of his life.
5. Universal Health Care
Hawking was a long-time advocate and champion of the UK's National Health Service (NHS).
"I wouldn't be here today if it were not for the NHS," Hawking told The Guardian.
"I have received a large amount of high-quality treatment without which I would not have survived."
Still, Hawking was seriously worried about the future of the NHS.
In an article for The Guardian titled "The NHS saved me. As a scientist, I must help to save it", Hawking argued that the NHS was being steadily destroyed by "underfunding and cuts, privatising services, the public sector pay cap, the new contract imposed on junior doctors, and removal of the student nurses' bursary."
In a 2017 speech at the Royal Society of Medicine, Hawking singled out Health Secretary Jeremy Hunt for leading the UK towards a "US-style insurance system."
In Hunt's campaign against the NHS, the Health Secretary claimed that 11,000 patients a year died because of understaffed hospitals on weekends.
Hawking was the first to point out that four of the eight studies Hunt cited were not peer reviewed. The physicist also listed 13 other peer-reviewed papers that completely contradicted Hunt's view.
"Speaking as a scientist, cherrypicking evidence is unacceptable," Hawking said.
"When public figures abuse scientific argument, citing some studies but suppressing others, to justify policies that they want to implement for other reasons, it debases scientific culture."
Despite all of Hunt's complaints, the NHS has been ranked as the best, safest and most affordable healthcare system out of 11 wealthy nations. Stephen Hawking is a testament to its brilliant work.