Tony Blair, prime minister, in the well-established tradition of hosts shaping the Group of Eight agenda, has determined that Africa and global climate change will be the focus of this year's gathering. These are both significant topics. Still, this year's G8 cannot limit what it does to these two areas, given all else that calls out for urgent attention.
The emphasis on Africa is justified. Humanitarian, economic and strategic arguments combine to make a strong case for G8 members providing greater assistance to promote development, to combat HIV/Aids and other infectious diseases and to deal with security challenges. Two caveats are worth highlighting, however.
The last thing anyone needs is for the G8 to degenerate into an argument about levels of aid. Left out of simplistic calculations are investment flows, debt forgiveness, help from charities and market access. More to the point, aid is just an input and can be of little import, or even counter-productive, if it simply perpetuates dysfunctional policies and is not accompanied by governance reforms.
Second, no discussion of Africa can be complete if it ignores the genocide taking place in Darfur in western Sudan. At a minimum, the G8 ought to increase and accelerate what it provides - intelligence, logistics, training, arms - to the force of the African Union.
The case for focusing on global climate change is less apparent, in spite of its significance. There is no consensus on what needs doing to slow the warming of the planet, something no amount of talk at Gleneagles will change. Also unclear is why now. The Kyoto protocol, which the US does not subscribe to and will not ratify, is due to run for another seven years. And any planning is difficult when it is far from clear that any technology or policy now available could make a substantial difference to the earth's temperature at an affordable cost.
What, then, should the eight be talking about? Trade would be a good place to start. A new global trade accord could boost the rate of economic growth in the countries of all those who attend. A US-European-Japanese agreement on a trade pact that phased out developed world subsidies and provided enhanced access to exports of developing countries could have far more economic impact than any amount of aid. A new trade deal would also contribute to the integration of emerging powers such as China, giving them an additional stake in regional and global stability while creating pressure on leaders to open up domestic politics further.
Discussion on two subjects from previous gatherings is incomplete. The first is nuclear non-proliferation. Much needed is a new international arrangement that would provide countries with access to nuclear fuel but bar them from control of it. The leaders should also agree on what Iran and North Korea should not be allowed to do and the fundamentals of a policy that could achieve that. The second topic that requires attention is Middle East reform, the main focus at last year's American-hosted summit. In the end, reform of the Arab world may be the best tack to promoting political stability in the region and to reducing the number of recruits to terror.
It would also be welcome if Mr Blair and his guests used some of the available time between formal meetings to have a word in private with Vladimir Putin, Russian president, who is scheduled to be the host of next year's get-together. Mr Putin should hear a consistent message that his programme of de-democratisation will scare off investors and, if it continues, raise questions about Russia's participation in future sessions of the G8.
This brings up a final subject that ought to be on Mr Blair's agenda: the G8 itself. The G8, with its emphasis on political and security matters as well as economics, fills an important niche. The problem is that the G8 is increasingly an anachronism. No one today would propose an annual meeting that includes Canada (population of 31m, gross domestic product of $870bn [£485bn]), Italy (58m and $1,200bn) and Russia (144m and $615bn) but not China (1.3bn and $1,650bn) and India (1.1bn and $650bn).
The G8 needs to become the G10. Both China and India deserve a seat. The question is whether Mr Blair, President George W. Bush and the others, who years ago extended membership to Russia, are again ready to open up their club. It would be a concession to reality that would benefit everyone.
The writer, author of "The Opportunity: America's Moment to Alter History's Course" (Public Affairs), is president of the Council on Foreign Relations .