Consider the classic hypothetical scenario: Your house is on fire and you can take only three things with you before the entire structure becomes engulfed in flames. What would you take? Laptops and external hard drives aside, people's responses to this question differ wildly. This diversity results from people's flexibility in ascribing unique value to objects ranging from a hand-scrawled note from a loved one to a threadbare t-shirt that others might consider worthless.

The critical quality that leads people to treat rookie cards like rosaries is that of the sacred, whereby an object becomes worthy of boundless reverence, commitment, and protection. Actually, it explains one side of the word "taboo" which few people realize. Taboo, the prohibition of an action based on the belief that such behavior is either too sacred and consecrated or too dangerous and accursed for ordinary individuals to undertake.

Generally, the prohibition that is inherent in a taboo includes the idea that its breach or defiance will be followed by some kind of trouble to the offender, such as lack of success in hunting or fishing, sickness, miscarriage, or death. In some cases proscription is the only way to avoid this danger; examples include rules against fishing or picking fruit at certain seasons and against walking or traveling in certain areas. Dietary restrictions are common, as are rules for the behavior of people facing important life events such as parturition, marriage, death, and rites of passage.

In other cases, the danger represented by the taboo can be overcome through ritual. This is often the case for taboos meant to protect communities and individuals from beings or situations that are simultaneously so powerful as to be inherently dangerous and so common that they are essentially unavoidable. For example, many cultures require persons who have been in physical contact with the dead to engage in a ritual cleansing. Many cultures also circumscribe physical contact with a woman who is menstruating—or, less often, a woman who is pregnant—because she is the locus of extremely powerful reproductive forces. Perhaps the most familiar resolution to this taboo is the Jewish practice of bathing in a mikvah after menstruation and parturition.

Taboos that are meant to prevent the sacred from being defiled by the ordinary include those that prohibited ordinary people from touching the head—or even the shadow—of a Polynesian chief because doing so would compromise his mana, or sacred power. As the chief's mana was important in maintaining the ritual security of the community, such actions were believed to place the entire population at risk.

There is broad agreement that the taboos current in any society tend to relate to objects and actions that are significant for the social order and that, as such, taboos belong to the general system of social control. Sigmund Freud provided perhaps the most ingenious explanation for the apparently irrational nature of taboos, positing that they were generated by ambivalent social attitudes and in effect represent forbidden actions for which there nevertheless exists a strong unconscious inclination.