life force
vital force
vitality *
elan vital

Are, it seems, is the only vital force left in his life.

Anyone who studies the history of life on Earth must come to respect death as a vital force.

She is the mother and on her rely all vital forces.

Women value the church's recognition that they are a vital force in the world.

He was the vital force that kept everything in existence.

Tiny was a vital force for many years in the development of this institution.

But world events, they acknowledge, are a vital force in the classroom.

The railroad was a vital force in the development of Portland.

The objects allow the family to maintain contact with the vital forces of nature.

There is a tension between two vital forces in education today: standards and equity.