Since ancient times, Eastern philosophy has embraced the idea of Ten–Jin Gōitsu—the unity of heaven and humanity.

At its core is the belief that all life is born from the greater forces of nature.

The natural world is often described as the “Greater Cosmos,” while the systems that exist within each individual life form are referred to as the “Lesser Cosmos.”

Every living being is governed by the greater cosmos and sustains itself by living in harmony with nature. Yet life is not entirely controlled by it. Each organism possesses its own inner world and unique functions. While encompassed by the greater cosmos, every life form remains organically connected as one of its essential elements.

Consider the cherry blossom. It blooms in full splendor each spring. This is not only because it is influenced by the seasonal forces of the greater cosmos, but also because within the cherry tree’s lesser cosmos exists an internal cycle—along with the ability to sense and respond to the arrival of spring.

Many biological phenomena undergo regular changes following inherent cycles. These cycles range from just a few seconds to nearly a year. Such temporal patterns are known as biological rhythms. What is particularly intriguing is that the rhythms found in humans closely resemble the environmental cycles of nature.

The circadian rhythm follows an approximately 24-hour cycle and is observed in sleep and wakefulness. The circaseptan rhythm spans about one week and has been observed in blood pressure patterns. The circatrigintan rhythm, lasting roughly one month, is characteristic of female hormone secretion. The circannual rhythm follows a yearly cycle—human sleep duration, for example, tends to increase in winter and decrease in summer.

The lesser cosmos is itself composed of many elements, each of which is also connected to the greater cosmos.

Research suggests that when humans live freely while disregarding the natural day–night cycle, the rhythm of sleep and wakefulness can become desynchronized from other rhythms such as body temperature and hormone secretion. When this synchronization is lost, both physical and mental imbalances are more likely to occur.

In Eastern medicine, ill health is believed to arise when the cycles of the greater cosmos and the lesser cosmos fall out of alignment.

From a scientific perspective as well, the principle of Ten–Jin Gōitsu—the unity of heaven and humanity—can be understood as a wise and effective path to well-being.