It is one of the common tricks of trade--when theologians argue upon the immortality of the soul, they bring and ring in any amount of biblical evidence to sustain them. They prove nothing. They cannot prove anything. It is the standing puzzle. They try to unravel a mysterious something that is not mysterious. Nor is there any need of mystery. What is essential for us to know is the truth, plain natural facts. There is nothing that we need be either ashamed or afraid of. If we have been deluded by errors made several thousand years ago, regarding the dual composition of man, or have been imposed upon and intentionally retarded in the onward progress, it is time to correct the error and remove the imposition. Let us have a clear, intelligent view of things and look at them as they are. This mystery, like other mysteries, can be cleared up by the light of science and modern investigation. What is the difference between man and animal? Articulate speech and the susceptibility of the brain matter to a high degree of culture. Mind is a term employed to designate the collective acquirements of a man's brain. In proportion as the acquirements are greater or less, the mind is greater or smaller. These acquirements may be simple, complex, or profound. They may be biased, general, or scientific; they may be deep, learned, or superficial. They may be only a slight advance above the general animal instinct; or may have assumed a superior intelligence and may have arisen to a higher plane of intellectual qualities. The acquirement or evolution of mental power and intellectual capacity depends: 1. On the constitutionally inherited capacity and capability. 2. On the size and general conformation of the brain. 3. On the perfect condition of the organs of special sense. 4. On the quality of the nervous structure. 5. On the general physical constitution of the body. 6. On the evenly balanced equilibrium between the vital organs. 7. On the chemical elementary constituents that enter into the composition of the various tissues, especially the nervous tissue. 8. And lastly on the education, training, or culture. 9. I may add, suggestively, on the relative quantity and quality of the gray and white substance of the brain, etc., and perhaps on the depth of the sulci and the size of the convolutions and the general symmetry of the different lobes of the cerebrum, etc. The brain of an idiot is not susceptible to culture or education. He has all the senses, but of an inferior and imperfect order; a brain insufficient in quantity and quality to be capable of acquiring anything. No mind can be formed. The idiot has not any intellect. Has he a soul? Or supposing any portion of the brain is diseased and any one of the special senses ceases to act, as sight, hearing, or any part of the muscular tissue, and the intellect is impaired, either partially or wholly incapacitated, then has the soul suffered any damage, or does the soul remain intact?