A week before the outgoing US President Barack Obama delivered his emotional and now much talked about farewell speech, he wrote a letter to his fellow Americans "on the progress we’ve made together” in view of the uncertainties ahead.

It was couched in characteristic hopeful and pragmatic tones wont of his eloquence.

"We will have to move forward as we always have — together,” he wrote, emphasising the patriotic fellowship "as a people who believe that out of many, we are one; that we are bound not by any one race or religion, but rather an adherence to a common creed; that all of us are created equal in the eyes of God.”

The words are reminiscent of his 2009 speech in Cairo in the precursor to the first Global Entrepreneurship Summit the following year, in which he reminded violent extremists that "we are shaped by every culture, drawn from every end of the Earth, and dedicated to a simple concept: E pluribus unum ‘Out of many, one.’”

It is for his moral authority he probably will be most remembered. No doubt, like many great leaders, the young Illinois senator who became the first black president of the United States at only 47 years old will be remembered in many ways, and will remain in mind as many things to as many people as will pay personal or other tributes.

In honour of his pliant demeanour and obvious moral flexibility, for instance, scientists have just named after him a tiny flatworm found in turtles’ blood, calling it Baracktrema obamai.

No matter the flatworm is a parasite, the naming is something of a paean or, more properly, a swan song to his legacy and the personal attributes he must carry forth which, as Time magazine put it, are like those of the "phenomenally incredibly resilient organism.”

For many East Africans, he will always be "our cousin-brother”, having been born of a Kenyan father. And, unless you are racist, no less from the intimate "interaction” such as a TV screen may allow, it will always be the sheer humanity and intelligence the man captivatingly exuded in his oratory in which he has carried most of us.

He leaves office aged only 55, but we should not expect he will be leaving the global stage just yet. Though he is yet to exactly define what shape citizen Obama’s life will take he is certain that the journey continues.

He may have spoken for America in the letter, but I will paraphrase him when he said, "However halting, however incomplete, however harshly challenged at each point on our journey  the story of [humanity] is a story of progress.”

It was an urge to all and sundry to give the incoming president the benefit of doubt and allow the man his chance. Humanity has always proved resilient, even in the face of incorrigible tyrants.

And, yet, President Obama was not perfect despite the goodwill in his oratory which, as one commentary observed, he "sometimes struggled to turn that poetry into the prose of governance.”

His role in the destruction of Libya will forever remain a blot in his legacy. And in the acerbic words of Professor Cornel West the often controversial Black American philosopher, author, critic, actor and civil rights activist – he lamented in The Guardian Obama’s "lapse of character in ordering drone strikes [that] unintentionally led to rightwing populist revolts at home and ugly Islamic fascist rebellions in the Middle East. And as deporter-in-chief nearly 2.5 million immigrants were deported under his watch w [how] Obama policies prefigure Trump’s barbaric plans.”

Prof. West’s is only one view. But history will judge Obama’s presidency for what it ultimately will be worth.

Here on the continent, his major legacy will probably be the Power Africa initiative that he launched in 2013, and assented into law under the Electrify Africa Act in February last year.

Of the expectation to light up the continent with more than 30,000 megawatts of power for more than 50 million people under the initiative, just a little over 4,000 megawatts have so far been generated.

We should hope the initiative goes according to plan.