How instinct can cheat you
There are something you believe instinctively but might not be correct. The complexity and symmetric of the universe inclines us to suppose a Creator that designed everything. However the truth is the universe and life on earth evolves by natural selection without any divine intervention. In his latest book The Delusion of God Richard Dawkins argues that our sense of religion and creator is an accidental by-product of our judgment and intuition of the external environment. Just like children like to ascribe purpose to everything, we all tend to think that the world was designed with a distinct purpose. This religious instinct is misleading us into believing in god.
On the contrary, there are also things that you reject instinctively (a heresy) might be true.
People think that the notion that we have sexual desire towards our parents are absurd and ridiculous. However the idea of Oedipus complex now has wide currency in explaining of the origin of the super-ego. According to Freud, during the phallic stage of a child’s psychosexual development, the infant will direct his sexual desire towards the mother. This process is important for the development of the normal sexual behaviours in the later stage of life.
When instinct fails
Instinct might be fallible and may not be a reliable guide in understanding the reality about ourselves. However they could be very useful in some areas thus conferring certain selective advantages necessary for the survival of the species.
On the same ground of Oedipus complex, people ask why we are not sexually attracted to our siblings. See Genetic sexual attraction. We tend to choose partner with similar level of education, background and upbringing, sharing the same sphere of life and hobbies but we never consider our siblings as one of the options. The reason is clear: it simply disgust us to think of having sex within the family members. Just like animals, human have a natural aversion to inbreeding. See Westermarck effect We will instinctively think that incest is wrong. There is a biological basis for not favouring incest because it will lead to an increase in homozygosity and an accumulation of deleterious recessive genes.
So what will happen when the instinct is not working? It is not surprise to find that parties involved in incest do not feel the guilt because they are not driven by the instinct (of aversion). In this respect we can deduce that: people don’t do incest not because we consciously choose not to, but we are refrained from doing so by our instinct. Using the same argument, for someone that have incestuous relationship, they don’t consciously choose to do so but there might be some defects in the protective instinct. They shall not be morally liable for that because they don’t have a say in this. Arguably this is a genetic defect that resulted in a psychosexual disorder.
Similar argument could be applied to homosexuality. You don’t have sex with people of the same sex not because you consciously avoid to, but it is the inbuilt biological mechanism that discourage that. Thus for somebody who is born gay, they do not make the choice of being gay but rather the protective instinct is malfunctioning.
However the biological defect conclusion is reached basing on the instinctive notion (again!) that heterosexual is normal and natural. But nature is somehow more complex than we think. In the animal kingdom homosexual behaviours are ubiquitous which arguably has some evolutionary advantage to minimize intraspecies aggression. Nature is rarely divisive (polymorphy) but rather there are normal distribution in all traits and inheritance e.g. height and weight. In this respect μ ± 2σ only defines the majority not the normality.