CONSERVATION.--THE RELATION OF GOD TO THE WORLD. (_Continued._) Of the various hypotheses which seek to dispense with the immediate agency of God, and to explain the conservation of the world by "secondary" or natural agencies, the second is that of _active Force communicated to matter at its creation_. This force being transformable, and at the same time indestructible, is regarded as adequate to the conservation of the universe. This hypothesis must not be confounded with the Dynamical theory of matter propounded by Leibnitz, and more fully elaborated by Boscovich, which regards matter as a mere phenomenon or function of force; on the contrary, it conceives of matter as a distinct entity moving under the action of a primary impulse communicated by "the Creator's fiat at the beginning." This hypothesis in its fundamental conception and its further elaboration is purely mechanical. It represents the universe as a machine first set in motion by the Deity, and conserved by the actions and reactions of its several parts. All subsequent motions, changes, and configurations are the prolonged results of the original impulse, without any further direct action or control on the part of the Creator. A more precise and accurate statement would require that the term "Energy" should be substituted for "Force." In the language of modern physics, _Force_ is "that which _originates_ or tends to originate motion or change," and "is _wholly expended_ in the action it produces."[255] All energy has its origin in force, but force can not pass into energy except under conditions in which it is at liberty to act. For instance, the _force_ of gravity produces the _energy_ of motion of a falling body, but gravity can not produce motion unless there is space through which the body can fall. _Energy_, therefore, is defined as "the power of doing work."[256] The work done is the resistance overcome, and in overcoming resistance the energy is transformed, but not annihilated. In every case in which energy is lost by resistance, heat is generated; and we learn from Joule's investigations that the quantity of heat generated is a perfectly definite equivalent for the energy lost. It is therefore claimed that the total quantity of energy in the universe is constant, and that the material system is dynamically conservative. The universe is a self-acting and self-sustained machine, and perpetual motion is a necessary consequence.