French philosopher and writer Jean-Paul Sartre (1905 to 1980) famously declared: "Man is condemned to be free."

This seems an odd thing to say.

Freedom is generally considered to be a good thing, something that people want and enjoy.

So what did he mean by saying that we are condemned to be free - as though freedom were something we would rather be without?

FREEDOM AND RESPONSIBILITY

Well, the trouble with freedom is that it brings responsibility.

When we choose and act freely, we must bear the responsibility for the consequences of our choices and actions - and this can be very burdensome.

In his short work, Existentialism And Humanism, Sartre illustrated this point with a real-life example - of a young man who, during the Nazi occupation of France in World War II, had to choose between his duty to his widowed mother and his duty to his country.

He wrote: "The boy was faced with the choice of leaving for England and joining the Free French Forces - that is, leaving his mother behind - or remaining with his mother and helping her to carry on."

If he remained in France to support and care for his mother, it would mean shirking his responsibility to fight against totalitarianism and injustice.

But if he left France to join the fight, it would mean deserting his mother - and perhaps sacrificing his own life uselessly.

Tormented by this dilemma, the young man sought Sartre's advice.

However, the only advice Sartre could offer was: "You are free, therefore choose."

At first sight, this seems an unhelpful and perhaps even a callous response.

But Sartre's point was valid.

The boy recognised two competing claims upon his life, and ultimately the responsibility to choose between them was his, and his alone.

He could ask for advice. But still he would have to choose whether to follow that advice or not.

His freedom was a grave and inescapable responsibility.

FREEDOM IS INESCAPABLE

According to Sartre, we are all free, every day of our lives, to choose what we will do and what we will become.

And for us, too, this is a grave and inescapable responsibility.

"We are condemned to be free," he said, "because once thrown into the world, we are responsible for everything we do."

We may try to hide behind labels.

For example, we may say, "I am a patriot, and therefore I must fight", or "I am a pacifist, and therefore I cannot fight".

But this does not let us off the hook. Because it is we who choose those roles.

The "patriot" is always free to say "on this occasion, I will not fight"; and the "pacifist" is always free to say "on this occasion I will fight".

If we fight for an unjust cause, then we bear the responsibility of fighting unjustly.

If we remain passive when our country is attacked, then we bear the responsibility of remaining passive.

HOPE AND OPPORTUNITY

Freedom, then, by Sartre's account, is a tremendous responsibility, an inescapable burden.

This all sounds rather bleak.

But there is a positive side to it, because freedom is not only a tremendous responsibility but also a tremendous opportunity.

Whatever our situation, whatever our history, we are always, Sartre insisted, free to choose what we will do next.

And this freedom provides us with an opportunity to change our situations and ourselves for the better.

We may feel that we have been weak or lazy or selfish or cowardly in the past. But we are free to redefine ourselves by choosing and acting differently in the future.

•Gary Hayden is a philosophy and science writer.