Here is a short definition of instinct in relation to fear by Roberto Assagioli:
There are five main forms of fear, and these underlie the five fundamental instincts:
– The first is the instinct of self-preservation, the root of which is the fear of death.
– The second is the sexual drive, arising from a sense of incompleteness and the fear of loneliness.
– The third is the herd instinct, again caused by the fear of being separated, weak, insecure. This fear causes us to seek support and security by associating with other people.
– The fourth is the tendency to affirm oneself. This might seem the total opposite of fear, but careful analysis shows that at least one of its roots is the fear of not being appreciated, recognized and respected as much as we deserve (or believe we deserve! ) and therefore not having the power we would like to have over others.
– The fifth is curiosity, the thirst for knowledge based on fear of the unknown or of mystery.
We have to acknowledge that these instincts or tendencies have spurred us on to useful, indeed necessary, activities, so even fear has had and can have a useful function. (Transpersonal Development, 2007, p. 164)