Charles S. Peirce
How to Make Our Ideas Clear
Popular Science Monthly 12 (January 1878), pp. 286-302
Public domain version, available at the website "Arisbe: Home of the Peirce Telecommunity" http://members.door.net/arisbe/arisbe.htm Transcription and markup:Joseph Ransdell and Brian Kariger
I (CP5.388, W3.257) Whoever has looked into a modern treatise on logic of the common sort, will doubtless remember the two distinctions between clear and obscure conceptions, and between distinct and confused (W3.258) conceptions. They have lain in the books now for nigh two centuries, unimproved and unmodified, and are generally reckoned by logicians as amongthe gems of their doctrine. (CP5.389) A clear idea is defined as one which is so apprehended that it will be recognized wherever it is met with, and so that no other will be mistaken for it. If it fails of this clearness, it is said to be obscure. This is rather a neat bit of philosophical terminology; yet, since it is clearness that they were defining, I wish the logicians had made theirdefinition a little more plain. Never to fail to recognize an idea, and under no circumstances to mistake another for it, let it come in how recondite a form it may, would indeed imply such prodigious force and clearness of intellect as is seldom met with in this world. On the other hand, merely to have such an acquaintance with the idea as to have become familiar with it, and to have lost all hesitancyin recognizing it in ordinary cases, hardly seems to deserve the name of clearness of apprehension, since after all it only amounts to a subjective feeling of mastery which may be entirely mistaken. I take it, however, that when the logicians speak of "clearness," they mean nothing more than such a familiarity with an idea, since they regard the quality as but a small merit, which needs to besupplemented by another, which they call distinctness. (CP5.390) A distinct idea is defined as one which contains nothing which is not clear. This is technical language; by the contents of an idea logicians understand whatever is contained in its definition. So that an idea is distinctly apprehended, according to them, when we can give a precise definition of it, in abstract terms. Here theprofessional logicians leave the subject; and I would not have troubled the reader with what they have to say, if it were not such a striking example of how they have been slumbering through ages of intellectual activity, listlessly disregarding the enginery of modern thought, and never dreaming of applying its lessons to the improvement of logic. It is easy to show that the doctrine that familiar use andabstract distinctness make the perfection of apprehension has its only true place in philosophies which have long been extinct; and it is now time to formulate the method of attaining to a more perfect clearness of thought, such as we see and admire in the thinkers of our own time. (CP5.391) When Descartes set about the reconstruction of philosophy, his first step was
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to (theoretically) permit scepticism and to discard the practice of the schoolmen of looking to authority as the ultimate source of truth. That done, he sought a more natural fountain of true (W3.259) principles, and thought he found it in the human mind;thus passing, in the directest way, from the method of authority to that of apriority, as described in my first paper. Self-consciousness was to furnish us with our fundamental truths, and to decide what was agreeable to reason. But since, evidently, not all ideas are true, he was led to note, as the first condition of infallibility, that they must be clear. The distinction between an idea seeming...