The object of this series is to furnish, in as popular a form as possible, a course of discipline for those who are beginning the study of philosophy. Strictly _popular_, in the sense the word is used—i. e. signifying that which holds fast to the ordinary consciousness of men, and does not take flights beyond—I am well aware, no philosophy can be. The nearest approach to it that can be made, consists in starting from the common external views, and drawing them into the speculative, step by step. For this purpose the method of definitions and axioms, with deductions therefrom, as employed by Spinoza, is more appropriate at first, and afterwards a gradual approach to the _Dialectic_, or true philosophic method. In the mathematical method (that of Spinoza just alluded to) the content may be speculative, but its form, never. Hence the student of philosophy needs only to turn his attention to the content at first; when that becomes in a measure familiar, he can then the more readily pass over to the true form of the speculative content, and thus achieve complete insight. A course of discipline in the speculative content, though under an inadequate form, would make a grand preparation for the study of Hegel or Plato; while a study of these, or, in short, of any writers who employ speculative _methods_ in treating speculative _content_—a study of these without previous acquaintance with the content is well nigh fruitless. One needs only to read the comments of translators of Plato upon his speculative passages, or the prevailing verdicts upon Hegel, to be satisfied on this point. The course that I shall here present will embody my own experience, to a great extent, in the chronological order of its development. Each lesson will endeavor to present an _aperçu_ derived from some great philosopher. Those coming later will presuppose the earlier ones, and frequently throw new light upon them. As one who undertakes the manufacture of an elegant piece of furniture needs carefully elaborated tools for that end, so must the thinker who wishes to comprehend the universe be equipped with the tools of thought, or else he will come off as poorly as he who should undertake to make a carved mahogany chair with no tools except his teeth and finger nails. What complicated machinery is required to transmute the rough ores into an American watch! And yet how common is the delusion that no elaboration of tools of thought is required to enable the commonest mind to manipulate the highest subjects of investigation. The alchemy that turned base metal into gold is only a symbol of that cunning alchemy of thought that by means of the philosopher’s stone (scientific method) dissolves the base _facts_ of experience into universal truths.