The first scientist to develop a convincing model of the interaction between psyche and soma was Walter B. Cannon, in his influential book The Wisdom of the Body, published in 1932. One of Cannon’s central ideas was that the body has an inherent “wisdom,” which consists of an exquisitely sensitive self-monitoring and self-regulating system centered in the hypothalamus that is constantly working to maintain the body in an optimal state of balance, harmony, equilibrium, stability. This optimal state, in which all parts and systems are interacting properly, is call homeostasis. Since the body is always changing and having to deal with changing conditions, any mechanism to keep the body in equilibrium must be able to maintain stability in the midst of flux, must respond with infinite adaptability to a constantly changing environment. In other words, homeostasis is relative: a process rather than a predetermined state.
Singular experience of floating in an enclosed tank does certain measurable things to your body, which in turn influences your state of mind; likewise, the tank experience has noticeable effects on your state of mind, which can produce numerous changes in your body. Neither exists without the other; they are not separate systems at all, but one system, united in a relationship of balance and interaction.
Why is the tank so effective in fostering homeostasis? If we see the mind/body as a single system, then it becomes clear that external stimuli are constantly militating against the system’s equilibrium: Every noise, every degree of temperature above or below the body’s optimal level, every encounter with other people, every feeling of responsibility, guilt, desire- everything we see and feel is incessantly interrupting, impinging on our self-contained system, causing it to expand energy to maintain its homeostatic balance. But when we enter the tank, our environment abruptly stops its constant alteration. The system is for once able to experience itself as a single, integral, unified entity. Since there are no external threats, no need to adapt to outside events, no deviations from the expected, the system can devote all its energies to restoring itself. It is as if we said Time out to the game of life, allowing our bodies to take a breather and restore themselves to normal. The normal state, of course, is health, vigor, enthusiasm, and immense pleasure in being alive.