Agni means "fire" in Sanskrit-the Creative Fire of the Universe. The fire god Agni is a major deity in the Vedic pantheon, especially in the Rig Veda. Agni and fire have a broad spectrum of meanings in the Agni Yoga books. They often refer to: the primordial light and life at the root of the universe; cosmic energy, or the "Fire of Space"; and "psychic energy," the powers of the human mind and heart, particularly those manifesting in love, thought, and creativity. In general, fire is a powerful transformative energy, a swift, subtle, connective force of high vibration.

Agni Yoga states that humanity is entering the New Era of Satya Yuga (Light), having just left the previous era of Kali Yuga (darkness) in which the flow of cosmic fire pouring onto the Earth will intensify. There is danger that the lack of spiritual synthesis (i.e. the inability of humanity to recognize the existence of Higher Fiery Energy Forces) will block these Energies from being transmuted by humanity into the crust of the earth where they would stabilize the molten magma under the surface. Without such transmutation by humanity, these energies wlll turn negative and destructive and bring on earthquakes and other upheavals. The situation is exacerbated by humanity’s misuse of "fire": not only such gross fires as combustion and electricity, but also the subtler fires of thought and feeling. If humanity and our planet are to survive, we need to be able to consciously accept this powerful energy from space and transform it into a constructive force. In accomplishing this, we first must purify and refine our psychic energy, the subtle force at the root of our emotions, perceptions, and thoughts. This gradual process involves expansion of consciousness, as well as the kindling of the subtle energy centers in the human organism and the transmutation of their fires.

Unlike most traditional approaches to the mastery of the highest subtle energies, Agni Yoga insists that mastery must take place within the context of contemporary secular life. Monasticism is replaced by action for the Common Good, creative work that helps build a new era based on knowledge that is both scientific and spiritual. Although "The coming epoch will be under the Rays of three Lords—Maitreya, Buddha, and Christ," the New Age is known as the Age of Maitreya, the future World Teacher, because the characteristics associated with Maitreya will come to the fore. Moreover, because the manifestation of Maitreya is linked with the affirmation of the Mother of the World, in the past, present and future," the coming era is also known as the Epoch of Woman, or the Epoch of the Mother of the World. It is also the Epoch of Shambhala, since humanity will be directly ruled by the Brotherhood of Mahatmas that dwell in Shambhala, a mysterious abode in Central Asia. "What are the signs of the time of Shambhala? The signs of the age of truth and cooperation." "One should understand the most proximate gifts of evolution: first—psychic energy; second—the woman's movement; third—cooperation. Each of these gifts must be accepted in full measure, not abstractly."

In addressing "builders and warriors," the very first lines of the Agni Yoga teaching indicate two aspects of the external work of those who follow Agni Yoga: construction of a New Era, and the battle to create conditions under which construction is possible.

The constructive work outlined in the Agni Yoga books embraces every domain of human life. In the first paragraphs of the Teaching, the work is likened to the building of a New Temple for all humanity, the temple being a symbol of spiritual knowledge. Art and beauty are also emphasized from the very beginning. "Remember, Art is the one vital medium of the coming culture. Through Beauty will you approach." Working with children is another early theme that continues through the entire series.

In the field of medicine, Agni Yoga anticipates developments in later decades. "Agni Yoga approaches just in time. Without it, who would say that epidemics of influenza should be cured by psychic energy? Who would pay attention to new kinds of mental illness, brain disease, and sleep disorders? …[O]ne should think seriously about the new enemies that are created by the conditions of contemporary life. One cannot apply the old methods to them; a new approach will be developed through the expansion of consciousness."

The new approach will focus on "psychic energy, because its crystal brings about the best healing. It is possible to extract deposits of this energy, which is a panacea for all illnesses." Just as an emotion like irritation gives rise to chemical substances that deposit in the body, so does the sacred energy, "because each energy has a physical crystal." Along with study of the "nerve centers" (chakras), research on the chemical deposits of subtle energies "will form the future direction of medicine. Through these domains humanity will come closer to detecting the subtlest energy, which for the sake of simplicity we call ‘spirit.’ The next step in the development of culture will arise from discovery of the emanations of this energy."

Agni Yoga favors empirical research on the interaction of psychic energy ("mind" or "spirit") with the human organism and its environment, and it often discusses how scientists might best approach this new field. At the same time, Agni Yoga endorses aromatherapy, Ayurveda, herbalism, suggestion, and other practices about which mainstream Western medicine remains skeptical. "We [of the Brotherhood] do not ignore the methods of Western science, but We lay psychic energy in the foundation. Having come to the conclusion that psychic energy is necessary both for ourselves and for experimental procedures, We are primarily concerned with creating conditions favorable to its accumulation."

The accumulation of psychic energy requires attention to the macrocosm (the physical atom) as well as the microcosm (the Higher Planes of Existence). The "course of the luminaries"—the motion of celestial bodies, particularly the planets that represent the seven lines of cosmic life—and the chemical composition of their rays have a powerful impact on human events. The ancient science of astrology should be revived, especially for medical and governmental purposes, but it needs to be combined with practical knowledge on the ground and the inner knowledge of a fiery heart. The expansion of consciousness will naturally carry humanity to the "far-off worlds," including planets on a higher plane of existence.

Agni Yoga’s insight into the Earth’s critical situation is ahead of its time. "People will ask, ‘Right now, how can we serve on Earth in the most beneficial way?’ They should restore the Earth’s health. There is a whole list of ways to carry out this worldwide task of restoration. One should keep in mind that people have destroyed the resources of Earth without mercy. They are ready to poison the earth and the air. They have laid waste forests—the receptacles of prana. They have diminished animal life, forgetting that animal energy nourishes the earth. They believe that untested chemical substances (medicine and drugs) can take the place of prana and earthly emanations. They plunder mineral resources, unmindful that a balance must be maintained. They do not think about what caused the catastrophe of Atlantis. They neglect the fact that chemical substances should be tested over the course of a century, for a single generation is too short to determine whether a substance will bring evolution or its opposite… They think that by some act of mercy the weather will clear and people will become prosperous! But the problem of restoring health does not cross their minds. So let us love all of creation!" There is also discussion of such issues as climate change, desertification, excessive urbanization, air pollution, and narcotics.