My English friend Paul Kingsnorth was the subject of a long article two weeks ago in The New York Times magazine, “It’s the End of the World as We Know It … and He Feels Fine.”

A former editor of The Ecologist, Paul has gained new attention of late for his passionate and public despair over “an age of ecocide” and his proclamations that we are now powerless to do anything about it. That expression of despair coincides with an equally public withdrawal from the battlefield of big-scale climate and environmental activism. He warns, “What all these movements are doing is selling a false premise. They’re saying, ‘If we take these actions, we will be able to achieve this goal.’ And if you can’t and you know that you are lying to people.”

We find ourselves at each step battling against powerful corporate forces pushing hard from the other side.

The article and his previous writings in the same vein have struck a resonant chord as the hard reality of what we face reveals itself, not in theories about the future but in the current realities of fierce storms, unprecedented droughts, mutating weather patterns, and a lack of political will to take strong action. More than 500 people left comments on the Times web site. A young activist who works with me at the Democracy Center, also from the U.K., emailed the article to her parents with a note saying, “This is exactly how I feel!”

The hard question that Paul Kingsnorth provokes is neither a new one nor is it only about the climate and environmental crisis. It has been a question inherent in political activism as long as there has been political activism: What action do we take when we have no guarantee at all that what we do will make any difference?

To be an activist is to plunge into the unknown and into a world where guarantees of results do not exist. On climate and the environmental crisis we don’t know how far we’ve already pushed the planet toward ecological Armageddon or what impact we actually have when we block coal trains, hold impassioned news events, or get arrested at the White House.

So we guess, and there are two different ways we can guess wrong. The first is to overestimate our power to change what’s coming and to give people the “false hope” Kingsnorth warns about. The second is to underestimate what is possible, to believe that we are less powerful than we actually are and to do less than we can. That’s the wrong guess that worries me more. Faced with a choice between disappointment or failing to do all that is possible, I don’t find the decision a hard one to make.

The dictionary defines hope as “to want something to be true and to believe that it can be.” Despite so much evidence and sentiment to the contrary, on the climate crisis I remain radically hopeful. I am hopeful because the fundamentals of what we need to do—abandon fossil fuels, protect the planet’s forests, and organize our communities for resilience—are not mysteries nor are they impossible. I am hopeful because I see among the young a powerful, rising culture of environmental consciousness, creativity and action that far surpasses any generation before it.

And I am hopeful because I’ve seen things happen that weren’t supposed to. A decade ago in the U.S. gay marriage was an issue Republicans put on ballots to bring out homophobic voters to the polls. Today it’s riding a juggernaut of support and inevitability.

What is truly possible never reveals itself until we take the risk to seek it.

That said, as an activist I am also radically realistic and action on climate is an especially hard case. Issues like gay marriage require changes of hearts and minds and public policy. Action on climate requires all that as well, and then on top of it we still face the great unknown of how nature will respond to the changes we are able to make. And as we press for action, we find ourselves at each step battling against powerful corporate forces pushing hard from the other side. There is no doubt that the challenge we face is enormous and that major ecological damage is now an inevitability. As Kingsnorth says, “Things that we value highly are going to be lost.”

It is easy to see how all this adds up to a crisis of hope at the heart of climate activism. To those activists, young and not so young, who feel this way, my message is just the opposite of Paul’s. Don’t retreat—step it up, and as we do keep these three things in mind.

First, we must be strategic. Citizen action and energy is too valuable a resource to waste. We must be realistic about where we are starting from, especially in terms of political support. We must be clear and smart about our goals and where we are trying to go. Then we need to develop plausible (not guaranteed) paths that have a real shot at taking us there, along with a commitment to making mid-course corrections in our strategies as we learn along the way.

Second, just as the world we seek to protect relies on natural biodiversity, we must respect that effective action requires “activism biodiversity.” Some of us will act locally, as Kingsnorth does now, teaching his neighbors how to wield a scythe and campaigning against construction of a local supermarket. Others will unmask the actions of fossil fuel companies, or chain themselves to trees, or campaign for more public transit, or take action in international forums. We need to do not one thing but all these things and more.

Finally, we must not let despair and resignation become the greatest gift we could ever hand to those who would love nothing more than for the climate movement to lose heart. Our truest strength does not come from any guarantee of outcome. It comes from the power of acting on our deepest convictions, of forming real community and acting together, and from knowing that what is truly possible never reveals itself until we take the risk to seek it.

Like Paul and others, I also mourn for what is being lost. I mourn most deeply on those days here in rural Tiquipaya when I awake to the roar of a chain saw and the wrenching thunder of a falling giant. What we can’t do is let that mourning stop us from doing all we can. As the labor activist and songwriter Joe Hill said on the eve of his execution a century ago, “Don’t mourn, organize!”