The tropical forest Indians believe that their well-being depends on being able to control innumerable supernatural powers, which in personal or impersonal form permeate or inhabit objects, living beings, and nature in general. Through shamanistic rites or collective ceremonies, humans must encourage and maintain their harmonious integration in the universe, controlling the forces that govern it; their beneficial or harmful effects are largely determined by human action. In most of the cultures, magical measures and precautions are more important than the religious cult as such. The strength and health of the body, the normal growth of children, the capacity to procreate, and even psychic qualities are obtained by magical means. For the individual these means may include the perforation of the lips, nasal septum, or ear lobes, the painting of the body, and the use of various adornments. A little stick passed through the nasal septum, such as that used by the Pawumwa of the Guaporé River, prevents sickness. The hunter or fisherman, in order to be successful and not to be panema (unlucky), as they say in many Amazonian regions, takes precautions such as scarring his arms or abstaining from certain foods. The magical devices of the hunter, the fisherman, and the warrior are considered much more important than their ability. Arrows must be treated by rubbing with a certain drug, since their magical attributes are believed to be more effective than their technical properties.

Stimulants and narcotics are of great importance in the magic and religious practices of most tropical forest Indians. Secular use of drugs is much rarer. Tobacco is known by almost all tribes. The Tupinamba shaman fumigates his rattle with tobacco, which he believes contains an animating principle that confers on the rattle the faculty of “speaking,” that is, of revealing the future. Alcoholic beverages, consumed mainly in religious festivals, are obtained by fermentation of manioc, corn, and other plants. They are unknown among the Ge, in the upper Xingu, and in some regions of Bolivia and Ecuador. Coca leaves are chewed, especially in the sub-Andean regions. Infusion of maté is taken in the Paraguay area, as well as by the Jívaro and other groups of Ecuador. Hallucinogens are used mainly in the Amazon–Orinoco area; they include species of Banisteriopsis (a tropical liana), from which is made a potion that produces visions. In certain tribes the use of this drug is restricted to shamanistic practices; in others, as in the Uaupés River area, it is an essential element in religious festivals in which the community revives its mythic tradition. Other narcotics in ritual use, among them the yopo, or paricá (Piptadenia), known among many northern groups, are often breathed in the form of snuff, which partners blow into one another’s nostrils; the Omagua of the upper Amazon used it as an enema.

Some magical practices are reserved for the shaman, who acquires status by natural endowment, by inspiration, by apprenticeship, or by painful initiation. The shaman may practice medicine, perform magic rites, and lead religious ceremonies. Rarely, however, is he a priest in the usual sense of the term. In many groups his influence is superior to that of the political chief; in some, as among the Guaraní, the two roles may coincide. Not uncommonly, his influence continues even after his death: in the Guianas and elsewhere, his soul becomes an auxiliary spirit of his living colleagues, helping them in their curing practices and in the control of harmful spirits; among the Rucuyen, the bodies of common individuals were cremated, while that of the shaman was kept in a special place so that his soul might live on.

In curing the sick, the shaman must remove the object causing the sickness: a small stone, a leaf, an insect, any substance that has been sent through the black magic of an evildoer. The cure consists of massages, suction, blowing, and fumigation. If the illness comes from loss of the soul, the shaman must search for and recover it. If it comes from a bad spirit, he tries to overcome the evil influence with the help of one or more auxiliary spirits.

The soul has its seat in the bones, the heart, the wrist, or in other parts of the body. Some Indians believe that two or more souls are responsible for various vital functions. One finds also the idea of a purely spiritual soul. The Guaraní believe that man has an animal soul governing his temperament and his instinctive reactions but that he also has a second, spiritual one, sent by a divinity at the moment of conception. Thanks to his second soul, man thinks, speaks, and is capable of noble sentiments. After death this second soul returns to live among the gods, while the other soul wanders the Earth as a ghost menacing the living.

Nature is believed to be peopled by demons and spirits that are beneficial or malevolent, depending on man’s behaviour. Besides the soul that gives life to every living thing, many plants and animals have a “mother” or “master,” as do manioc, maize, and game animals.

The mythology of almost all tribes includes a creator of the universe and of people. This creator seldom sustains interest in his handiwork, and thus there is usually no cult attached to him. Social institutions, customs, knowledge, techniques, and cultivated plants are deeds or gifts of a culture hero or a pair of them, sometimes twin brothers who may represent the Sun and Moon. A number of myths are told about these figures; sometimes the pair consists of a hero and a trickster who opposes him.

Ceremonial practices vary, depending on the tribe and its way of life. Some great collective ceremonies have been associated with war, as among the northern Carib and the coastal Tupí, both famous for cannibalism, and the headhunting Mundurukú and Jívaro. Ceremonies are often believed to be indispensable for regulating the course of the Sun and the Moon, the sequence of the seasons, the fertility of plants, the procreation of animals, and the very continuity of human life. Their objective may also be to commune with the dead or with mythical ancestors; when they are connected with the disposal of the dead, they are at the same time passage rites, by means of which the spirits of the dead are made harmless. Among the Guaraní, most religious ceremonies mean profound spiritual communion with the gods.

Corpses are commonly disposed of by ground burial within or without the house. Urn burial has also been known, especially among Tupí groups; some groups have been known to unearth bones, clean them, and then rebury them. The Tarariu (Tarairiu) of northeastern Brazil and some Pano broiled the flesh of their dead and mixed the pulverized bones and hair with water or with a manioc-base beverage that they drank. Tribes of the Caribbean coast, after drying the body by fire, allowed it to decompose and later added the powder to a drink. In other northern regions, one still finds the custom of cremating the cadaver and consuming the charred and crushed bones in a banana mush.

Artistic efforts are most commonly applied to decoration, whether of the human body, objects of practical or ritual use, or even houses. The most common body adornments are paint and feather ornaments. Tattooing has also been practiced, especially among the Mundurukú and many Arawak tribes. Magical and religious ideas are usually expressed in these adornments. The Carib tribes of the Guianas and some Tupí were outstanding in featherwork. The plumed mantles of the Tupinamba, the delicate and elaborate adornments of the Caapor of Maranhão state, and the rich and varied ones of the Mundurukú are much celebrated.

The design of ornaments is almost always geometrical, with characteristic patterns for particular tribes; the styles vary with the cultural areas.

Masks, generally used in ceremonial dances, are restricted to the tribes of certain areas: the Guartegaya and Amniapé (Amniepe) of the upper Madeira, the tribes of the upper Xingu, the Karajá and the Tapirapé of the Araguáia River area, some Ge of central Brazil, and the Guaraní of southern Bolivia. The masks represent the spirits of plants, fish, and other animals, as well as mythical heroes and divinities. They are highly stylized in form but, on occasion, naturalistic in expression.

The Waurá women of the upper Xingu are famous for their pots and animal-shaped bowls. Of the historic tribes, the Tapajó of the Amazon had the richest style in ceramics, excelled only by the archaeological remains of the Ilha de Marajó. Among some groups in the Guianas and western Amazonia, artistic activity includes wood carving.