countless separate activities involved in the normal process of an organism's physical maturation. Organic self-
regulation is the indisputable, fascinating, and challenging phenomenon at the base of the science of biology.
Life exists on different levels of development and complexity, from the single cell to man. As life advances from
simpler to higher levels, one may distinguish three forms or categories of self-regulatory activity, which I shall
designate as: the vegetative level of self-regulation—the conscious-behavioral level—the self-conscious level.
The vegetative level is the most primitive. All the physiological-biochemical processes within a plant, by which the
plant maintains its own existence, are of this order. This pattern of self-regulatory activity is operative within a
single cell and in all higher life forms. It is operative in the non-conscious physiological-biochemical processes
within the bodies of animals and men—as in metabolism, for example.
The conscious-behavioral level of self-regulation appears with the emergence of consciousness in animals. The
vegetative level continues to operate within the animal's body—but a new, higher level is required to protect and
sustain the animal's life, as the animal moves through its environment. This level is achieved by the animal's power
of awareness. Its senses provide it with the knowledge it needs to hunt, to move around obstacles, to flee from
enemies, etc. Its ability to be conscious of the external world enables the animal to regulate and direct its motor
activity. Deprived of its senses, an animal could not survive. For all living entities that possess it, consciousness —
the regulator of action—is the basic means of survival.
The sensory-perceptual level of an animal's consciousness does not permit it, of course, to be aware of the issue of
life and death as such; but given the appropriate physical environment, the animal's sensory-perceptual apparatus
and its pleasure-pain mechanism function automatically to protect its life. If its range of awareness cannot cope
with the conditions that confront the animal, it perishes. But, within the limit of its powers, its consciousness serves
to regulate its behavior in the direction of life. Thus, with the faculty of locomotion and the emergence of
consciousness in animals, a new form of self-regulatory activity appears in nature, a new expression of the
biological principle of life.