Your soul is your essence as a human being. When you were conceived, if you believe in God, He shot a bolt of lightning into you that made you unique and original.
He endowed you with gifts, talents and weaknesses that made you who you are or at least who you are spozed to be if you're smart enough to escape the brainwash of the world.
If we were created by Nature, the outcome is still the same. I'm no different than the cat I play with every night. I watch him to observe him being himself, following his true nature. He is me in a different form, a living being following his true nature but this is where most of humanity gets off the boat – they don't follow their true natures.
Leonardo Da Vinci said vitality and beauty are gifts of nature for those who live according to its laws and he was right. The only true purpose of life is to follow your true nature. All the wise, enlightened people who have ever lived live by this rule.