It does not lie within the scope of this essay to enter upon the practical application of the principle which we have set forth as the criterion of truth. One hint only may be supplied, to point out the most obvious maxim derivable from it—a maxim that is instinctively obeyed by all scientists and has often been popularly expressed in the sentence: An ounce of fact is worth a hundred pounds of hypothesis, or of any interpretation of facts. All the theories in the world, scientific and economical, our dearest ideals not excepted, and all the most ingenious hypotheses have no value unless they have been derived from, and agree with, the laws that live in the facts of our experience. The trouble of applying this rule lies mainly in the difficulty of distinguishing between facts and our interpretation of facts. Considering that mind is representativeness in feelings we have to analyse the mind in order to come down to objective facts. The percept of a tree is not the tree; it is an interpretation of a group of facts; it is a mental picture produced by a synthesis of sensations, the latter being caused by sense-impressions. Considering that all the images, ideas, abstract concepts, and theories of which our mind consists are not the facts represented by them but their several interpretations, we at once see how careful we have to be for purposes of philosophical and scientific exactness in the statement of facts. * * * * * On this occasion, a few critical remarks concerning the leading essay of this number, "The Architecture of Theories," by Mr. Charles S. Peirce, may be added. Mr. Peirce is one of our subtlest thinkers and logicians, and it is incumbent upon one to reflect twice before criticising any sentence of a man who writes upon the most recondite topics,—upon what I should call the higher mathematics, the differential and integral calculus of logic,—with ease and masterly accuracy. Mr. Peirce's essay "The Architecture of Theories,"[55] presented in this number of _The Monist_, is the first publication of his in which he propounds not mere criticism or the discussion of abstruse logical subjects, but his own positive opinion, presenting in great and clear outlines the foundations of his philosophy. [55] The term "architecture of theories" seems inappropriate from the standpoint of a positive conception of the world. Many monisms have been constructed in the way Mr. Peirce so well describes in his comparison of these philosophical systems to the building a house of one and the same material, for instance _papier mâché_, with roof of roofing paper, foundations of paste-board, windows of paraffined paper, etc., etc. Philosophy, however, is not a construction of a theory comparable to the building of an edifice; it is rather the mapping out of the house in which we live for the purpose of orientation.