There is a famous story about friendship in the Talmud. It is the story of Rav Yochanan and Resh Lakish, unlikely study partners whose daily interaction and give and take was so deep and meaningful that when Resh Lakish died, Rav Yochanan was thrown into bitter mourning and passed away soon afterwards. The friendship and relationship was life-sustaining.

This ancient sentiment has been confirmed recently by numerous studies. (see: What are Friends For? A Longer Life in NY Times, April 21,2009) Strong friendships lead to greater success in battling illness and to greater vibrancy in general. Friendships promote brain health and psychological well-being. And without friends...the converse is true.

Friends are a crucial support system, not just in sorrow but also in joy. What's good news without someone to share it with?

Yet there is a price. The mishnah in Ethics of our Fathers says "Buy for yourself a friend." This is not referring literally to a financial transaction; it's referring to time and effort.

A friendship requires give and take. If it is all one or the other it is not a friendship. It may be a relationship you want to maintain for other reasons, but it is a delusion to call it friendship.

Like a marriage, friendship demands commitment.

Like a marriage, friendship demands commitment. It requires saying "I'm there for you" and meaning it.

Which is why, Facebook to the contrary, most of us have very few friends. It is simply not possible to invest the time and effort and emotion necessary to create true friendship in large numbers of people.

Nor is it wise. Although CNN thought it was breaking news that Ashton Kutcher was the first to reach 1,000,000 Twitters, I was surprised it was considered newsworthy at all. It may say something about star power; it says nothing about real relationships.

And successful friendships share another common trait with successful marriage. They require common goals and a shared sense of purpose.

It may not be that hard to find someone to see a movie with but it is significantly more difficult to find someone who will help you out when you're in trouble and stand by your side through thick and thin.

Many years ago a friend of ours who was a prominent local philanthropist was sentenced to some time in jail for a relatively minor white collar crime (I'm not justifying the crime, merely explaining the circumstances). All of the sudden no one in any of the organizations that had been feting him would return his calls. Only my husband and a very few others bothered to visit him in prison.

Because they require so much time and effort, real friendships are rare. Because they require so much energy and attention, real friendships are precious. And, as the Talmud and recent studies demonstrate, life-sustaining and affirming.

Well worth the price.