With the explosive growth of biology, biological data accumulate in an increasing rate. At present, theoretical biology does not have its fundamental principles that could offer biological insight. In this situation, it is advisable for biology to learn from its older brother, physics. The most powerful tool of physics is the action principle, from which all the fundamental laws of physics can be derived in their most elegant form. We show that today’s physics is far from utilizing the full potential of the action principle. This circumstance is almost inevitable, since it belongs to the nature of the physical problems that the endpoint of the action principle is fixed already by the initial conditions, and that physical behavior in most cases corresponds to the minimal form of the action principle. Actually, the mathematical form of the action principle allows also endpoints corresponding to the maximum of the action. We show that when we endow the action principle with this overlooked possibility, it gains an enormous additional power, which, perhaps surprisingly, directly corresponds to biological behavior. The biological version of the least action principle is the most action principle. It is characteristically biological to strive to the most action, instead of manifesting inert behavior corresponding to the least action. A fallen body in classical physics cannot select its endpoint. How is it possible that a fallen bird can select the endpoint of its trajectory? We consider how the photon “selects” its endpoint in the classical and the extended double-slit experiments, and propose a new causal interpretation of quantum physics. We show that “spontaneous targeting” observed in living organisms is a direct manifestation of the causally determined quantum processes. For the first time, we formulate here the first principle of biology in a mathematical form and present some of its applications of primary importance. We indicate that the general phenomenon of biological homing relies on long-range cooperative forces between biomolecules, including mechanical, electromagnetic and osmotic forces. We show how theoretical biology beyond the quantum level can shed light to the properties of elementary consciousness.

least action principle; most action principle; biological foundations of quantum physics; quantitative framework for theoretical biological physics