Final Words
Self-deception has a number of benefits, chiefly in saving a person from facing a truth that is painful - the painful truth might be an attitude toward a person, group, object, situation, or whatnot - but it is in essence an attitude held by a person, and therefore it is always about the person who holds the attitude, not the object of that attitude.
Self-deception is generally seen to be a dysfunctional, but is at times necessary to avoid being prevented by anxiety or grief from doing what is necessary to survive and prosper. In this sense, self-deception can be enabling rather than disabling.
There are also certain side-effects of some of the ego defenses, particularly those regarded as "mature" that are beneficial to the individual. For example, asceticism causes a person to reconsider long-standing patterns of behavior with the possibility at arriving at a new and better appreciation of life - sorting out the trivial things to which they had given too much attention and effort an finding a higher purpose in life that will ultimately lead to greater satisfaction and happiness.
Even seemingly detrimental or annoying defenses such as dramatization and grandiosity can lead a person to channel their negative energies into positive and productive pursuits, the benefit of which outweigh the detriments of self-deception. Arguably, Leonardo da Vinci's refusal to accept his homosexuality resulted in channeling his efforts into art and invention, and have been of greater benefit to society than if he had simply accepted his desires and settled into a quiet life with a same-sex partner and did nothing remarkable.
Considering the potential benefits, self-deception is not categorically to be discouraged. It is only when self-deception prevents a person from taking some necessary or beneficial action that it becomes dysfunctional. This typically occurs when the deception causes a person to avoid something that needs to be addressed (and can be addressed) or when the side-effects of the deception (anxiety and fear of its discovery) have a similar effect.
Over time, self-deception can undermine a person's sense of self, and the positive qualities of character that enable them to take proactive measures to maintain and improve their lives in a functional manner - at which point the defense mechanism becomes a mental disorder, likened to a disease that spreads through the mind, wreaking havoc.
Nearly every person is deceiving himself about something, and some deceive themselves about a great many things - and this remains perfectly healthy until it becomes disorderly. Changes in an individual's behavior are indicative of their status: whether their deceptions are helpful or harmful, and particularly when there is a change in state from one to the other, such that the individual is "on the brink" of a mental breakdown.
It's also noted that ego defenses arise because of an individual's personality, as it is before the painful emotions arose and required suppression or denial. Not everyone who experiences a tragic loss can turn lemons into lemonade - some find a functional outlet, some are simply crushed, and much depends on the person as they were before the tragic loss occurred.
Some theorists (particularly Trivers) have taken the extreme position that natural selection favors self-deception because it enables a person to cope rather than collapse. It also gives people the ability to deceive others, in that they gain experience through the deception of themselves. When a stigmatized individual can deceive others into ignoring his stigma, his social interactions are facilitated. And if he should coach or provide a model for others, then even more benefit from his self-deception. To teach a Jewish person to act like a non-Jew in a society that is hostile to people of that faith is beneficial, given that society cannot be so easily changed.
However, this is not to say that self-deception is always good, merely that it is not always bad - and there are generally more detriments than benefits.
Self-deception presents an individual with a distorted and unrealistic perspective of reality, and impairs his ability to think rationally, to reach correct conclusions, and to make sound and effective decisions. More often than not, a decision based on skewed or incorrect information is inferior to one made with full awareness of facts.
Self-deception is also socially detrimental, as a person may more easily deceive himself than others. Those who recognize the self-deception are likely to consider the individual to be unreliable or untrustworthy, and to avoid social interaction and especially any connection at which the deception might pose a risk. There is also the negative halo effect that causes others to have a broader sense of doubt: "if he is deluded about this, what else might he be deluded about?"
Self-deception also spreads mental illness to others. Consider the man who carries frustration home from work to inflict his anger upon his family: his wife and children suffer significant negative consequences from his behavior, and may develop mental illnesses of their own.
The author returns to Greek philosophy, and the tenet of knowing oneself. To know and accept one's own true nature is considered to be the basis of happiness and perfection in life and to achieve a state of calm and lucidity called "ataraxia," of freedom from unnecessary distress and worry that allows the mind to be focused on the present, and to plan effectively for the future.
Self-deception is not the path to tranquility, but to constant distress and worry, which results in a cornucopia of other psychological disturbances: anger, irritability, inability to concentrate, insomnia, nightmares, compulsiveness, inflexibility, and other negative behaviors. A person who deceives himself has an incomplete account of reality, and an inability to make effective decisions. As a result, his life choices will be suboptimal, as will his life.
Weighing the benefits against the detriments, the author feels that self-deception must be regarded as more harmful than helpful in the long run. It is only useful in exceptional situations and for a brief period of time - much as a crutch can defend a broken leg until the bone heals, but can deform the body if it is used longer than necessary.
It is, in effect, a form of mental blindness that prevents us from appreciating the world such as it is, or achieving all that is possible in life - and as such, the author does not believe there can be any choice but to avoid and disarm it insofar as we are able.