We do not presume to say that these metaphysical speculations are either futile or improper. But what we do insist upon, and beg the reader distinctly to note, is that these speculations are neither _scientific_ nor _religious_, and that neither true science nor true religion is responsible for them. They are not religious, even though indulged in by theologians; because religion is solely concerned with the personal consciousness of our relation to God, and the discharge of our personal duty to God, and not in the remotest sense with any theory as to the method of causation in the world around us. It is equally certain that these speculations are not scientific, even though indulged in by scientists; because science deals only with phenomena, and the laws of phenomena; and it is a fundamental canon of all scientific induction that no problem is to be mooted unless it can be presented in terms of experience, and no principles are to be admitted which can not be verified by experiment. But the modern speculations respecting the _origin_ of motion, of life, and of mind can not be presented in terms of sensible experience, and can not be verified by actual experiment. So far as sensible experience goes, every case of physical motion is a transformation of energy, and every new physiological unit or aggregation of units is derived from pre-existent bioplasm. And so Dr. Tyndall, in the speculations in which he indulges, in the now celebrated "Inaugural Address" delivered at Belfast, particularly in regard to the origin of life, admits that he "_oversteps the boundary of the experimental evidence_;" therefore, by his own admission, these speculations are _unscientific_.[414] These discussions are inevitable, and even valuable. We would protest as earnestly as Dr. Tyndall against the attempt of any man to set limits to human thought, but we would equally protest against the attempt to pass off the results of speculative thinking in any direction as "exact science." True science is itself dishonored and discredited by all such attempts. We have said that it is solely within the field of speculative thought that all controversy has arisen concerning the doctrine of special providence and the efficacy of prayer. This will be apparent from the consideration of the fact that from the dawn of speculative thought to the present hour two radically opposite theories of the origin of things have prevailed--one _mechanical_, the other _vital_.