Kofi Annanis about to retire after 10 years as United Nations general secretary. He looks at the challenges that lie ahead.
Nearly 50 years ago, when I arrived in Minnesota as a student fresh from Africa, I had much to learn - starting with the fact that there is nothing weird about wearing earmuffs when the temperature is 15 below. All my life since has been a learning experience.
Now I want to pass on five lessons I have learnt during the past 10 years - lessons which I believe the community of nations needs to learn, as it confronts the challenges of the 21st century.
First, in today's world we are all responsible for each other's security. Against such threats as nuclear proliferation, climate change, global pandemics, or terrorists operating from safe havens in failed states, no nation can make itself secure by seeking supremacy over all others.
Only by working to make each other secure can we hope to achieve lasting security for ourselves.
But when we look at the murder, rape and starvation still being inflicted on the people of Darfur, we realise that such doctrines remain pure rhetoric unless those with the power to intervene effectively are prepared to take the lead.
Second, we are also responsible for each other's welfare. Without a measure of solidarity, no society can be truly stable. It is not realistic to think that some people can go on deriving great benefits from globalisation while billions of others are left in, or thrown into, abject poverty.
Third, both security and prosperity depend on respect for human rights and the rule of law. Throughout history human life has been enriched by diversity. But if our communities are to live in peace we must stress also what unites us: our common humanity, and the need for our human dignity and rights to be protected by law.
Both foreigners and a country's own citizens are more likely to invest when their basic rights are protected and they know they will be fairly treated under the law.
My fourth lesson is that governments must be accountable for their actions. Every state owes some account to other states on which its actions have a decisive impact.
As things stand, poor and weak states are easily held to account, because they need foreign aid. But large and powerful states, whose actions have the greatest impact on others, can be constrained only by their own people. States can no longer - if they ever could - confront global challenges alone.
How can states hold each other to account? Only through multilateral institutions. So my final lesson is that those institutions must be organised in a fair and democratic way, giving the poor and the weak some influence over the actions of the rich and the strong.
Developing countries should have a stronger voice in international financial institutions, whose decisions can mean life or death for their people. And new permanent or long-term members should be added to the UN Security Council, whose current membership reflects the reality of 1945, not of today's world.
More than ever today, humanity needs a functioning global system. And experience has shown, time and again, that the system works poorly when its member states are divided and lack leadership, but much better when there is unity and far-sighted leadership and engagement of all major actors.
This article is based on an address Kofi Annanis due to give today at the Truman Presidential Museum & Library in Independence, Missouri