When reciting the declaration of the unity of God, we are required to commit ourselves to this belief, that in the event we were coerced to deny Him, we would surrender our lives rather than do so. This concept is called mesiras nefesh, and in addition to our belief in God, there are only two other instances where we are to choose martyrdom rather than transgression: murder and adultery.
While the thought of surrendering one's life is frightening, it has unfortunately characterized much of Jewish history. However, since the urge for survival is innate and most intense and generally overrides all other considerations, how can so many Jews have risen to the challenge of mesiras nefesh?
The answer is quite simple. Just think of what life would be like if nothing was worth dying for: no ideals, no principles, no loyalty, no sacredness, no ultimate value. Under duress, everything would go. Could thinking people who pride themselves in living on a plane of life higher than that of brute beasts see any value in this kind of life?
There are things that are dearer than life that give life its great value.