Final Gnosis: Plato's The World's Soul

'And he made her out of the following elements and on this wise: Out of the indivisible and unchangeable, and also out of that which is divisible and has to do with material bodies, he compounded a third and intermediate kind of essence, partaking of the nature of the same and of the other, and this compound he placed accordingly in a mean between the indivisible, and the divisible and material. He took the three elements of the same, the other, and the essence, and mingled them into one form, compressing by force the reluctant and unsociable nature of the other into the same.'

Fear is the element described here as one of the three elements; hunger, lust and fear. Without it we, Life, would still be 'unchangeable'.