It is believed that, though this small volume embraces most of those points in metaphysics which have been considered the most difficult, there is not a page that can not be perfectly comprehended by any man or woman of only an ordinarily good education, and with less intellectual effort than is demanded of little girls in acquiring an ability to parse the English language. It is true that _close thought and attention_ are requisite for a full appreciation of all in this volume; but not more of these are required than the dignity and importance of the great topics involved properly demand. In attempting what is here proposed, it can be seen that there are great difficulties to be met. As a general fact, these subjects have not been presented in popular forms, but have been confined to works of metaphysics and theology, and there enveloped in scientific techniques and formulas not interesting or intelligible to the common mind. For this reason, it has been suggested that, before presenting the abstract portion, a _practical illustration_ of the subject, embodied in the history of the opinions of the author, as they have been formed or modified by these principles, would have far more effect on the class of readers for whom the work is written than the bare statement of principles and argument, while it would certainly be more likely to be read. It has been still farther urged that, in attempting to controvert long-established theories, embodied as a part of religious truth in the popular mind, there will be an opposition of _feeling_ to be overcome, which needs a counterbalancing appeal to the feelings such as an individual history can best offer. As to the propriety of such a measure, it is now so common to offer autobiographies, and histories of life and opinions by living authors, that this will be no innovation on the customs of the literary world. To this, a more weighty consideration should be added, and that is, that all questions of propriety and of duty are regulated by circumstances of risk and danger. A woman, suddenly roused from sleep to save her children from the flames, has a very different rule of propriety in appearing before the public from that demanded on ordinary occasions. In this view, a believer in the risks of the _eternal loss of the soul_ must withhold nothing, however sacred and cherished, if there is the shadow of a probability that it will avail aught in aiding, it may be, but one struggling, darkened mind in the death-agony of the soul. From these considerations, the writer has been led to prefix to the exhibition of principles and arguments of this work, a mental history that shall particularly illustrate the subjects discussed. The article was prepared for certain personal and family friends, and is inserted very nearly in its original form. ILLUSTRATIVE MENTAL HISTORY.