Wakeful Dreams: on Fears and Courage.
Fear was born the same moment we stepped on the path to self-knowledge. Fear is a diapason of frequencies with a specific length of wave that ego generates in reaction to the unknowable. Love and owe are the other diapasons. The difference between them is in the amplitudes. The effect of fear is contraction, it folds the wave onto itself piling up which is best described with the Fibonacci sequences; the effect of love is expansion, it amplifies the wave outwards exponentially which is best described by the “Flower of Life” with the vectors of flow proceeding in toroidal shape.
Knowledge contains fear since the boundaries of knowledge hold the uncertainty. To know that you don't know breads fear, to know that you know instills caution, to don't know that you don't know is a bliss. Fear is the quality of mind (not just brain). The sense of entitlement to have certainty is the cause of fear. Knowledge fears the unknown, knowledge has something to loose – itself, because the Unknown can shatter the Known. For, there exist no fear where there is nothing to loose, where the unknown is the domain rather then venture. To be childlike is to have no fear, to be blissful is to have no fear. But to know that you know nothing is courage. Courage is a quality of the heart, not the mind, courage literally means 'core' – the heart.
Courage, therefore, is to willingly act from the premise of the unknown, from the surmise of nothing to loose – moving from the partiality of the mind into the wholeness of the heart.
Caution on the other hand, is both, the island of safety and the prison island. Being a product of knowledge gained through experience it serves as a pillar of safety, yet works as a chain and ball to those aspiring growth and adventure.
Figuratively, apple eaten from the tree of knowledge brought people from the state of bliss into the state of fear. Why has it happened – is another topic, but to say the least, it was a necessity, a predetermined course of events.
You also say that there is a deeper fear, a fear below the surface of reason. You are right, almost an animal fear. It is monumental, like the underwater part of an iceberg; however, this fear is also knowledge-based, except that knowledge is not personal but hereditary. It reveals itself through subconscious channels and the deeper it dwells the less explainable it is. Some may go as deep as cultural and evolutionary imprints; species-specific memories appearing on cellular level and embedded inside the thus called natural instincts. Personal knowledge is only the surface, but 'the knowledge' is always where fears take roots. That's why worry precedes fear which is also contagious because knowledge is often 'shared' among those of the same kin, group etc.
To overcome fear, one needs to centre emotions in the heart. Heart, being the middle chakra, is a magnetic centre. Fear cannot propagate when balance is reached, for fear like knowledge is and has always been an illusion.