Swedenborg was born at Stockholm. His father, Jesper Swedberg, was a prominent member of the Swedish clergy, court chaplain, professor of theology in the University of Uppsala, and later bishop of Skara. When the family was ennobled in 1719, it took the name Swedenborg. After graduating from the University of Uppsala in 1709, the young Swedenborg spent five years abroad. He had become fascinated by mathematics and the natural sciences, and to study them he visited England, Holland, France, and Germany, meeting some of the representatives of the new sciences there and learning practical mechanical skills. Swedenborg's inventive and mechanical genius flowered at this time, and his speculations ranged from a method of finding terrestrial longitude by the Moon to new methods of constructing docks and even to tentative suggestions for the submarine and the airplane.

He returned to Sweden in 1715 and soon began to publish that country's first scientific journal, called Daedalus Hyperboreus, in which he wrote numerous reports of his projects and discoveries and of the inventions of Sweden's foremost mechanical talent of the time, Christopher Polhem. King Charles XII made the young scientist an assistant to Polhem by appointing him assessor extra ordinem (“extraordinary”) at the Royal Board of Mines. In this office, and later as assessor, he devoted himself for 30 years to the development and improvement of Sweden's metal-mining industries. At this time he devoted several years to publishing reports and treatises on various scientific and philosophical problems—e.g., cosmology, corpuscular philosophy, mathematics, and human sensory perceptions. Now and then he also found time to write poems in Latin, some of which were published. In 1718 he published the first work on algebra in the Swedish language, and in 1721 he published a work on chemistry and physics.

Swedenborg was ennobled in 1719. After a second journey abroad in 1721–22, during which he published two Latin volumes on natural philosophy and chemistry, he wrote little or nothing for more than 10 years. But when he set out for a third European journey in 1733, it became obvious that these years had been filled with reading and reflection in addition to his ordinary work as a civil servant. In 1734 he published in Leipzig his Opera Philosophica et Mineralia (“Philosophical and Logical Works”) in three folio volumes, the first of which, the Principia Rerum Naturalium (“Principles of Natural Things”), contains Swedenborg's mature philosophy of nature. In this work he reached by inductive argument several conclusions that resemble the theories of modern scientists. Swedenborg posited that matter consists of particles that are indefinitely divisible, and that these particles are in constant vortical (swirling) motion. Furthermore, these particles are themselves composed of smaller particles in motion. This idea strongly resembles the modern conception of the atom as described in terms of a nucleus and its electrons. Swedenborg's suggestion concerning the formation of planets in the solar system was a precursor of the Kant–Laplace nebular theory (i.e., that the Sun and planets come from a common nebula).

Investigation of “the Kingdom of the Soul.” After he published the Principia and a small work on the infinite in 1734, Swedenborg returned home. His father died in 1735, and in the next year he was granted a new leave of absence from his office as assessor. This time he went to France, Italy, and Holland. In Amsterdam he completed and published a new work in two great volumes, called Oeconomia Regni Animalis (1740–41; The Economy of the Animal Kingdom), and in November 1740 he was back in Stockholm.

Oeconomia Regni Animalis represents a new stage in Swedenborg's scientific career. As he had sought to find the “soul” of creation in pure motion, he now sought to understand the soul of man and to find it in its own kingdom—i.e., the body. Here Swedenborg made a thorough study of human anatomy and physiology, with special attention to the blood and the brain. But he was not studying the human body as a subject per se. What he intended was to fulfill a program that he had formulated in 1734—i.e., to prove the immortality of the soul to the senses themselves. He believed the soul to be the inmost life of the blood and located in the brain, specifically in the cellular cortex. Swedenborg's method as a researcher consisted mainly in collecting facts from microscopists and experimentalists and drawing his own conclusions from them. His energy and his erudition were overwhelming, and he has been given credit for some contributions to the localization of the mental processes. His anatomical works, however, remained almost unnoticed by contemporary science, and, when they were discovered by some 19th-century scholars, science had moved beyond them. Oeconomia Regni Animalis was followed by a whole series of sketches and small treatises in which Swedenborg attempted to round out his psychological investigations. Some of these became a part of the three volumes of the Regnum Animale (The Animal Kingdom, 2 vol.)—planned to be 17 volumes—that Swedenborg himself published in 1744–45.

These years of anatomical research were concluded by a painful religious crisis from which there survives a unique document. It is usually called the Journal of Dreams (1743–44) and was obviously meant to be a journal of his new travels beginning in July 1743, but the rather trivial notices were suddenly interrupted. There follows instead a list of various dreams recalled from earlier years and a detailed report on his spiritual experiences, mostly at night, from March to October 1744. Some of the dreams were of a grossly sexual character and caused many pious readers quite a shock when the journal was published in 1859. But the feelings of guilt Swedenborg evidently experienced at this time were not concentrated on his sexual impulses but rather on his intellectual pride, his burning ambition to be recognized as a great man of science. On April 7, 1744, he had his first vision of Christ, which gave him a temporary rest from the temptations of his own pride and the evil spirits he believed to be around him. A definite call to abandon worldly learning occurred in April 1745, Swedenborg told his friends in his later years. The call apparently came in the form of a waking vision of the Lord. Swedenborg thereafter left his remaining works in the natural sciences unfinished.

For the remainder of his long career, Swedenborg devoted his enormous energy to interpreting the Bible and to relating what he had seen and heard in the world of spirits and angels. From 1749 to 1771 he wrote some 30 volumes, all of them in Latin and the major part anonymously. Among these were Arcana Coelestia, 8 vol. (1749–56; Heavenly Arcana) and Apocalypsis Explicata, 4 vol. (1785–89; Apocalypse Explained), which contain his commentaries on the internal spiritual meaning of Genesis and Exodus and on the Book of Revelation, respectively. De Coelo et ejus Mirabilibus et de Inferno (1758; On Heaven and Its Wonders and on Hell) is perhaps his best-known theological work. He gave an admirably clear summary of his theological thinking in his last work, the Vera Christiana Religio (1771; True Christian Religion), which was written when he was 83.

Swedenborg asserted that his entry into the field of theological study was in response to a divine vision and call; that his spiritual senses were opened so that he might be in the spiritual world as consciously as in the material world; and that the long series of exegetical and theological works that he wrote constituted a revelation from God for a new age of truth and reason in religion. Furthermore, he held that this new revelation of God was what was meant by the Second Coming. Because of his otherworldly experiences, Swedenborg has often been regarded either as a spiritualist “medium” or as a mystic, but in his dry, matter-of-fact accounts of the spiritual world and in his acutely reasoned theology he actually retains his lifelong attitude of the scientific and philosophic investigator.

Swedenborg consistently maintained that the infinite, indivisible power and life within all creation is God. In his theology he asserts the absolute unity of God in both essence (essentia) and being (esse). The Father, the Son, and the Holy Spirit represent a trinity of essential qualities in God; love, wisdom, and activity. This divine trinity is reproduced in human beings in the form of the trinity of soul, body, and mind. Swedenborg accepted that all creation has its origin in the divine love and wisdom and asserted that all created things are forms and effects of specific aspects of that love and wisdom and thus “correspond,” on the material plane, to spiritual realities. This true order of creation, however, has been disturbed by man's misuse of his free will. He has diverted his love from God to his own ego, and thus evil has come into the world.

In order to redeem and save mankind, the divine being of God had to come into the world in the material, tangible form of a human being—i.e., Jesus Christ. Christ's soul partook of the divine being itself, but in order that there might be an intimate contact of God with fallen mankind, Jesus assumed from Mary a body and a human nature comprising all the planes of human life. During the course of his life on earth, Jesus resisted every possible temptation and lived to their divine fullness the truths of the Word of God; in so doing he laid aside all the human qualities he had received from Mary, and his nature was revealed as the divine embodiment of the divine soul. Redemption, for Swedenborg, consisted in mankind being re-created in God's image through the vehicle of Christ's glorification. It was through the example of Christ's victory over all temptation and all evil that men could achieve a similar harmonious unification between their spiritual and their material aspects. Swedenborg rejected the tripersonalism of the orthodox doctrine of the Trinity (i.e., the one God revealed in the Persons of Father, Son, and Holy Spirit). To him the Trinity was in one Person, the Father being the originating divine being itself, the Son the human embodiment of that divine soul, and the Holy Spirit the outflowing activity of Jesus, or the “Divine Human.”

Swedenborg also rejected the orthodox conceptions of redemption. To him the redemption of mankind represented a deliverance from the domination of evil. The hells, which are the communities of the spirits of evil men in the spiritual world, were aspiring to force themselves upon men's minds, destroying their freedom to discern between truth and falsity and therefore between good and evil. By admitting into himself the evil spirits' temptations and by his complete resistance to them, Jesus broke their power; and the inflowing of the divine being into the human plane thus perfected interposed an eternal and infinitely powerful barrier between the hells and mankind. Human beings are thus saved from the forcible imposition of the hells upon themselves and are thus free to know and obey the truth. Man's salvation depends on his acceptance of and response to divine truth.

In his massive exegetical and theological volumes, Swedenborg attempted to interpret the Scriptures in the light of the “correspondence” between the spiritual and the material planes. He viewed references in the Bible to mundane historical matters as symbolically communicated spiritual truths, the key to which he tried to find through detailed and voluminous commentaries and interpretations. Swedenborg died in London in 1772, where he was buried in the Swedish Church. At the request of the Swedish government, his body was removed to Uppsala cathedral in 1908.

Swedenborg never acted as a preacher but rather relied totally on the effect of his huge Latin volumes. The first Swedenborgian societies appeared in the 1780s, and the first independent congregation, the origin of the various Church of the New Jerusalem organizations, was founded in London by the end of that decade. Swedenborg's influence was by no means restricted to his immediate disciples. His visions and religious ideas have been a source of inspiration for a number of prominent writers, including Honoré de Balzac, Charles Baudelaire, Ralph Waldo Emerson, William Butler Yeats, and August Strindberg. His theological writings have been translated into many languages, and there is a constant flow of new editions.