In my previous column, I said there are many men and women who are saddened and disquieted by a nagging sense that their lives lack meaning.
They may lead comfortable lives.
They may have good jobs and loving families.
But still, they find themselves asking: What is it all for? Where does it all lead to?
Since then, I have received a number of e-mail messages from Mind Your Body readers who struggle with this problem.
Some of them describe the unhappiness this feeling of meaninglessness brings to their lives.
Others express hope that I will offer some enlightenment or advice in this week's column.
Sadly, I cannot offer any enlightenment.
But I can offer some encouragement and, perhaps, a little advice.
A London cabby once recognised one of his passengers as the celebrated poet T. S. Eliot.
As he drove along, he said to Eliot: "I've got an eye for a celebrity. The other day, I picked up that famous philosopher, Bertrand Russell.
"I said to him, 'Well, Lord Russell, what's it all about?' And, do you know, he couldn't tell me!"
The taxi driver may have been surprised that a philosopher of Russell's stature could not tell him the meaning of life.
But I am not.
On the contrary, it would surprise me if Russell had been able to give a clear and simple answer to such a deep and difficult question.
In any case, the truly important question is not the general "what is the meaning of life?" but, rather, the very specific question of "what makes my life meaningful?".
The Austrian psychiatrist and Holocaust survivor Viktor Frankl (1905 - 1997), who dedicated his life to helping depressed and suicidal patients find meaning and purpose in their lives, once wrote: "Questions about the meaning of life can never be answered by sweeping statements.
"'Life' does not mean something vague, but something very real and concrete, just as life's tasks are also very real and concrete."
He was right. We are all unique.
We face different problems and encounter different opportunities. We possess different talents and are motivated by different desires. We have different hopes and different fears. We have different histories and operate under different sets of circumstances.
Our challenge, then, is not to find some abstract meaning of life, but rather to find specific goals and tasks which will bring a sense of meaning to our individual lives.
Frankl puts it like this: "The meaning of life differs from man to man, from day to day and from hour to hour.
"What matters, therefore, is not the meaning of life in general but, rather, the specific meaning of a person's life at a given moment."
WORK, LOVE, COURAGE
So what does Frankl have in mind? What kind of things bring meaning and purpose to individual lives?
In his book, Man's Search For Meaning, he identifies three possible sources of personal meaning: work, love and courage.
The following example illustrates two of these.
During his time as a prisoner in the Nazi concentration camps of World War II, Frankl encountered many fellow prisoners who had lost their will to live.
Two men, for example, talked of their intention to commit suicide, arguing that they had "nothing more to expect from life".
To help them, Frankl had to convince them they still had a reason to live; that although they expected nothing more from life, life still expected something more from them.
Both men eventually came to realise they did indeed have something to live for.
For one of the men, that "something" was his son, who was still alive and waiting for him in a foreign country.
For the other man, it was his work.
He was a scientist who had begun writing a series of books which nobody but himself could finish.
So one man found meaning in love; and the other man found meaning in work.
In my final column on this subject, in two weeks, I will discuss more about work and love as sources of meaning.
I will also explain the role of courage in a meaningful life.
Gary Hayden is a philosophy and science writer.
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