All living creatures have a strong, even overwhelming urge to continue living; yet our entire ecosystem would collapse without universal mortality (every living thing dies); thus, there is a basic paradox at the hear of the living cosmos.
Human beings are animals, first and foremost, sharing completely in the evolution of species on this earth, and large chunks of human emotions, social life and basic physical and nervous makeup reflect that shared animal heritage.
Human beings have the intelligence to think abstractly; this is in essence what sets human psychology and cognition apart from animal psychology and cognition (This is the most general statement of human uniqueness, but only humans have many ending propositions in literature, e.g., have a concept of zero, have language, do mathematics, understand negation, practice religion, etc. All of these and many more would be seen as cases in point of the ability to think abstractly).
Because it is rooted in the ability to think abstractly, human cognition is able to grasp the paradoxical Mortality Principle on which our ecosystem/cosmos is based at the deepest levels, and feel it intensely qua paradox.
The most important features of human psychology are born out of the clash between the overwhelming urge to continue living and the cognitive awareness of universal mortality; this recognition of the inevitability of the death (the paradoxical Mortality Principle) creates a reservoir of potentially immobilizing, debilitating anxiety.
There are defense mechanisms in individual psychology (e.g., denial, repression, projection, displacement, dissociation, rationalization, intellectualization, identification, reaction formation, sublimation, humor. There are more than 20 in the specialized literature). Each of these mechanisms manifests itself in creative and destructive forms.
Likewise, there are social defense mechanisms, habitual patterns of collective behavior aimed at defending established social formations (ritual, scapegoating, segregation, denigration, assimilation, annihilation, etc.). Each of these mechanisms manifests itself in creative and destructive forms.
The entire array of individual and social defense mechanisms are regularly employed to maintain individual and social equanimity in reaction to threats of death, and also in reaction to the symbolic threats of death contained in recognition of the cosmic Mortality Principle. Such defense mechanisms probably originated in, but certainly were strategically contoured in their contemporary form by, this need for anxiety control in the face of mortality awareness. In short, our highly developed intelligence caused the anxiety problem in the first place, and also comes forth with at least the provisional solution to the anxiety problem.
One very central and ubiquitous anxiety-compensatory movie is to transfer the urge for continued living from the physical realm to the symbolic realm; the organismic urge for continued living becomes channeled into the urge for immortality in the symbolic realm.
The urge for symbolic immortality is the source of very large chunks of human creativity and life-affirming energies; it is the underlying function of culture/religion to serve as venues through which people achieve and maintain a sense of participation in symbolic immortality (soul survival, larger-than-life projects, etc.).
All cultures/religions are on the one level fictional, since t hey all promise something (immortality) on which they cannot deliver; however, they are all also potentially true, in that each provides some functional viability for anxiety-compensation. Human individual and social life without such fictions would be unbearable and impossible.
There is power in numbers; the more you rub shoulders only with people who believe in the same cultural/religious fictions, the more plausible those fictions become (we all tell the same stories!).
People who do NOT share our cultural/religious assumptions (stories, fictions) are a big problem, since by their very existence the cast doubt n the absolute certainty of our truth (revealing its fiction nature to us) and thus expose us again to the repressed anxiety they function to allay in the first place.
Hence, culturally/religiously Dissimilar Others may be a creative source for helping us widen and enhance our own vision; or, they may be encountered in the most literal sense, as enemies.
Modern, post-Darwinian human beings are more likely in the first place to suspect the fictional character of their cultural/religious stories/truths than those of previous generations, and this is further aggravated because improvements in communications and travel technology force moderns to confront the reality of the culturally/religiously Dissimilar Other on a regular basis.
Future human well-being, and possibly even simple human survival, will depend on learning to substitute more creative manifestations of the individual and social defense mechanisms against the anxiety provoked by the religiously/culturally Dissimilar Other for the more destructive manifestations.