It's one of the great mysteries of life and now a Coventry academic has been given a five-figure sum to try and solve it - how souls work.
Melody Stokes, from Fillongley, near Coventry, has been awarded a £27,250 fellowship for her year of soul-searching.
The 48-year-old mother-oftwo, a research fellow at De Montfort University, in Leicester, has been given the funding to research the human spirit.
She said she would combine her background in mechanical engineering and work on energy patterns to attempt to understand how and why we think and feel the way we do. She said she became determined to explain the spirit inside the body to understand the behaviour of her son, who was struggling at school.
The former mechanical engineer with Lotus Cars will investigate the way the body uses energy and how thoughts and feelings can be seen as "patterns of energy bursts in our minds and bodies".
She said: "I want this to be a proper explanation of life from a scientific point of view. I'm an engineer and engineers are essentially practical people.
"We like to put things in order.
"I want to take this analogy of how energy flows in cars but applied to people, to understand the essentials of how we work."
She admitted people might be "spooked" by the idea of trying to explain away their soul but added: "In understanding how a car works, I still drive from A to B like everyone else.
"Knowing how the engine works simply adds to my enjoyment of driving.
"People are like cars. They're formed from a multitude of tiny systems in which the energy ebbs and flows.
"But they're also like cars in another way, in that no two of them are ever alike. I want to begin to explain things like why we suddenly burst into tears, how we can predict when we're going to get ill, or when we're going to be in a bad mood."
Ms Stokes became interested in understanding what makes us tick while working for her PhD on patterns of electricity demand.
She received a call from her son's school teacher, concerned about his unpredictable behaviour in the classroom.
"I've always been interested in how people think and feel, and I was trying to work out my son's pattern of behaviour and the things which might cause him to react in certain ways," she said.
"And suddenly, while I was looking at these models of electricity demand, I wondered whether it would be possible to model people's behaviour too.
"I'm going to be looking into things like neuroscience, biochemistry, psychology, even quantum theory and the Big Bang. It's a real challenge for me."