Utility

Life is the opposite of death, like motion is the opposite of stillness. So life is all about doing, so it's all about optimizing a function that as humans we call "utility", which is the measurement of the capacity to do with efficiency.

• why do other people act like that? Because it's useful for them.
• why do we see that bacteria motion/behaviour? Because it's useful for her.
• why do a big forest fire is sad? Because it brings stillness where motion was.
• etc...