Carter endorsed the blueprint Iran presented to the United Nations Security Council. Pretty much every civil war ends with some version of Iran's four-step proposal: ceasefire, unity government, constitutional reforms and a supervised election. In crediting Iran with this bland proposal, Carter is implicitly acknowledging that Iran and Russia will get the credit for ending the war, the "unity government" will not involve any real power-sharing, the constitutional reform will be mostly cosmetic and President Bashar Assad's re-election is a foregone conclusion.

Carter envisions Russia and Iran forcing a deal on Assad that is far better than he deserves, while the U.S. forces Saudi Arabia and Turkey to end their support of extremists in the region. The "win" for Russia and Iran, in combination with the American arm-twisting needed to realize Carter's plan, will change the geopolitical future of the region. It may even jeopardize America's longstanding relationship with Saudi Arabia, creating another opportunity for China to expand its arms sales and influence.

Given these costs, how can this plan be ethical and strategic?

The heart of the problem is that even with American training, drone attacks, logistical support, weapons and U.S. Special Forces, the more moderate Syrian opposition cannot win. The Obama administration has tried a "support the moderates" strategy for three years, achieving less than the Chicago Cubs in their effort to win the World Series. Russia's entry into the Syrian conflict assured Assad's victory, but the rise of the Islamic State group had already revealed the futility of the U.S. strategy.

It is neither ethical nor pragmatic to stick to a failed strategy, especially because most of the non-Islamic State group Syrian opposition still alive and fighting is not, in fact, moderate, respectable or competent enough to justify American support. (The Kurds and a few other ethnic groups are important exceptions, and ensuring their protection must be a central focus during any five-nation negotiations.) 

There are three ethical and interest-based reasons to support Carter's plan. First, the flow of refugees from Syria is a destabilizing humanitarian disaster. Half of Syria's population is seeking refuge around the world. Europe cannot absorb Syrian refugees without fomenting a political backlash that will destabilize European and world politics for years to come. We must deal with the refugee crisis at its source.

Next, the Islamic State group openly endorses slavery, genocide and sectarian conflict around the world and for this reason it must be defeated. Ignoring it as it gains strength by practicing its medieval vision of Islam is just plain stupid.

Lastly, the U.S. wars in Iraq and Afghanistan have already taught us the cost of backing weak, inept governments that pursue their own sectarian strategies. Does the U.S. seriously want to prop up yet another set of questionable allies, this time in Syria?

Hans Morgenthau, the father of political realism, warned great powers to divest their foreign policy of a crusading spirit, not let weak allies set their agenda and be willing to compromise all issues that are not vital to them. From the opposite end of the political spectrum, Stanley Hoffmann, an advocate of political liberalism, recognized that where a policy is hopeless, restraint from action is the more ethical choice.

We need to chose the side of the people, which means doing what it takes to end Syria's civil war and defeat the Islamic State group. The pill will be bitter, but continuing the civil war in Syria is even worse.