Yet even as Carlyle eulogized his Great Men, there emerged an alternative: the earnest heroism of middle-class virtue. Where the Renaissance hero achieved greatness in battle and the Romantic hero turned his back on society, the 19th century hero quietly did his duty. As the Leeds-based lecturer Samuel Smiles put it in his global best seller, Self-Help, "Many are the lives of men unwritten, which have nevertheless as powerfully influenced civilization and progress as the more fortunate Great whose names are recorded in biography." And in recording the lives of such men as engineers James Watt and Richard Arkwright, Smiles aimed to do just that. Heroism had become democratized. It was a history of earnest, unpublicized endeavor which caught the imagination of one of my own heroes, John Ruskin. "The wonder has always been great to me," he wrote in 1864, "that heroism has never been supposed in anywise consistent with the practice of supplying people with food, or clothes; but rather with that of quartering one's self upon them for food, and stripping them of their clothes." This special issue continues to honor that vision, by recognizing several heroes who seek to bring staples of Western life to those who lack them. As the democratic 20th century dawned, there was an ever stronger emphasis on those whom history forgot. For the traditional marks of heroism had passed over the worthy lives of millions. Some seemed even to believe that every human being was intrinsically heroic. The late 19th century Russian anarchist Alexander Herzen suggested that it was "quite enough to be simply a human being, to have something to tell."

Virginia Woolf — daughter of Leslie Stephen, editor of that Victorian celebration of heroism, the Dictionary of National Biography — was moved to remark: "Since so much is known that used to be unknown, the question now inevitably asks itself, whether the lives of great men only should be recorded. Is not anyone who has lived a life, and left a record of that life, worthy of biography — the failures as well as the successes, the humble as well as the illustrious? And what is greatness? And what smallness?" It was up to modern biographers to set up new standards of merit and "new heroes for our admiration."

As the century progressed, many felt the need to reject heroism altogether. Carlyle's Great Man had morphed into Nietzsche's Super-Man with calamitous global consequences. The warmongering of European statesmen led novelist E.M. Forster to condemn hero-worship as "a dangerous vice." For Forster, one of democracy's merits was that "it does not … produce that unmanageable type of citizen known as the Great Man," but "produces instead different kinds of small men — a much finer achievement."

Small heroes seemed absolutely necessary in the face of Adolf Hitler. Just as the philosophers of the Frankfurt School physically fled their native land, so too did the thinkers of the mid-century flee from the idea of equating militarism with greatness. Even during wartime, George Orwell felt able to write in 1944, "The English people have no love of military glory and not much admiration for great men." Orwell did not ascribe to heroism semidivine greatness or classical virtus; instead he admired "a moral quality which must be vaguely described as decency."

Heroism today is even more complex. The transparency that mass media demands means that personal foibles can, in the public imagination, often overshadow great acts: today, John F. Kennedy is as much remembered for his love life as for the achievements of his presidency. The cult of celebrity often threatens to undermine true heroism; while these pages contain their share of celebrities, they have used their fame to further the public good.

Perhaps most problematic is that few modern Western states are homogeneous societies instinctively able to rally around "national heroes." (Because this edition is published throughout Africa and the Middle East, we've included heroes from those regions as well.) An educated, multicultural citizenry rarely shares a unified benchmark of heroism — which is why this issue singles out a French woman of Algerian descent fighting for women's rights and a half-Turkish, half-Kurdish man who's been persecuted for trying to preserve Kurdish music. At the same time, when a country's star athlete wins an Olympic medal after years of struggle, how many among us can fully resist sharing the national pride?

That tension is precisely why the consensual search for modern heroes is all the more important. And so TIME has chosen a definition of heroism based on merit and humanity; one that seeks to record the often forgotten achievements of an unremarked public; one that values overcoming adversity and celebrates selfless acts to help others. We think it's an appropriately 21st century reflection of history's shifting sands. And when you've read this year's profiles, we hope you'll agree.