A critical comparison of the countless and manifold fantasies which belief in immortality has produced during the last few thousand years in the different races and religions yields a most remarkable picture. An intensely interesting presentation of it, based on most extensive original research, may be found in Adalbert Svoboda's distinguished works, _The Illusion of the Soul_ and _Forms of Faith_. However absurd and inconsistent with modern knowledge most of these myths seem to be, they still play an important part, and, as "postulates of practical reason," they exercise a powerful influence on the opinions of individuals and on the destiny of races. The idealist and spiritualist philosophy of the day will freely grant that these prevalent materialistic forms of belief in immortality are untenable; it will say that the refined idea of an immaterial soul, a Platonic "idea" or a transcendental psychic substance, must be substituted for them. But modern realism can have nothing whatever to do with these incomprehensible notions; they satisfy neither the mind's feeling of causality nor the yearning of our emotions. If we take a comprehensive glance at all that modern anthropology, psychology, and cosmology teach with regard to athanatism, we are forced to this definite conclusion: "The belief in the immortality of the human soul is a dogma which is in hopeless contradiction with the most solid empirical truths of modern science." CHAPTER XII THE LAW OF SUBSTANCE The Fundamental Chemical Law of the Constancy of Matter--The Fundamental Physical Law of the Conservation of Energy--Combination of Both Laws in the Law of Substance--The Kinetic, Pyknotic, and Dualistic Ideas of Substance--Monism of Matter--Ponderable Matter--Atoms and Elements--Affinity of the Elements--The Soul of the Atom (Feeling and Inclination)--Existence and Character of Ether--Ether and Ponderable Matter--Force and Energy--Potential and Actual Force--Unity of Natural Forces--Supremacy of the Law of Substance The supreme and all-pervading law of nature, the true and only cosmological law, is, in my opinion, _the law of substance_; its discovery and establishment is the greatest intellectual triumph of the nineteenth century, in the sense that all other known laws of nature are subordinate to it. Under the name of "law of substance" we embrace two supreme laws of different origin and age--the older is the chemical law of the "conservation of matter," and the younger is the physical law of the "conservation of energy."[23] It will be self-evident to many readers, and it is acknowledged by most of the scientific men of the day, that these two great laws are essentially inseparable. This fundamental thesis, however, is still much contested in some quarters, and we must proceed to furnish the proof of it. But we must first devote a few words to each of the two laws.