Experimental physics has succeeded, during the last decade of the century, in reducing all gaseous bodies to a liquid--most of them, also, to a solid--condition. Nothing more is needed than special apparatus, which exerts a violent pressure on the gases at a very low temperature. By this process not only the atmospheric elements, oxygen, hydrogen, and nitrogen, but even compound gases (such as carbonic-acid gas) and gaseous aggregates (like the atmosphere) have been changed from gaseous to liquid form. In this way the "invisible" substances have become "visible" to all, and in a certain sense "tangible." With this transformation the mystic nimbus which formerly veiled the character of the gas in popular estimation--as an invisible body that wrought visible effects--has entirely disappeared. If, then, the substance of the soul were really gaseous, it should be possible to liquefy it by the application of a high pressure at a low temperature. We could then catch the soul as it is "breathed out" at the moment of death, condense it, and exhibit it in a bottle as "immortal fluid" (_Fluidum animae immortale_). By a further lowering of temperature and increase of pressure it might be possible to solidify it--to produce "soul-snow." The experiment has not yet succeeded. If athanatism were true, if, indeed, the human soul were to live for all eternity, we should have to grant the same privilege to the souls of the higher animals, at least to those of the nearest related mammals (apes, dogs, etc.). For man is not distinguished from them by a special _kind_ of soul, or by any peculiar and exclusive psychic function, but only by a higher _degree_ of psychic activity, a superior stage of development. In particular, consciousness--the function of the association of ideas, thought, and reason--has reached a higher level in many men (by no means in all) than in most of the animals. Yet this difference is far from being so great as is popularly supposed; and it is much slighter in every respect than the corresponding difference between the higher and the lower animal souls, or even the difference between the highest and the lowest stages of the human soul itself. If we ascribe "personal immortality" to man, we are bound to grant it also to the higher animals.