The writings of Charles S. Peirce are a rich source of conceptual analysis and innovation; yet, the complexity of his terminology may cause frustration and bewilderment. He worked on his philosophical and scientific vocabulary throughout his life. Peirce took this task seriously, even devising a special ethics of terminology for philosophical and scientific discourse. He strived for clarity, but refused to simply settle for the means provided by the philosophy and everyday language of the time. The result is an original and living - but occasionally daunting - set of terms, consisting of neologisms, concepts resuscitated from the history of philosophy, and special uses of common words.
     The Commens Dictionary of Peirce's Terms consists of original quotations, in which Peirce defines or characterises his technical terms. This collection of quotes does not lay claim to completeness; nor does it provide an introduction to Peirce's philosophy. The dictionary offers representative samples of Peirce's terminological definitions. It is intended to serve as an aid for researchers and students.
     The dictionary has been compiled according to the following set of principles:

• All definitions and characterisations are by Peirce himself; editorial input is limited to the selection and highlighting of relevant quotations, in addition to abbreviations of certain passages (marked with brackets).
• The dictionary does not attempt to synthesise the various definitions or explain variations in Peirce's terminology; secondary comments are separated from the main entries and open up in new browser windows (requires javascript).
• Terms are identified and individuated by the actual words used. That is, different words are treated as different terms, except in cases where synonymy is deemed to be beyond all doubt and no significant differences can be ascertained in Peirce's use of the different words.
• Attention is paid to Peirce's conceptual development; the quotations are listed in reverse chronological order. Passages from undated manuscripts are placed last.
• Anyone can suggest additions or corrections to the dictionary, but the editors reserve the right to select and edit the entries.

     The selection of the passages is determined by their definition-like character. Thus, the focus is on texts in which Peirce explicitly discusses his terms; other passages are included only if they clarify Peirce's terminological usage.
     Because the dictionary is selective, it is bound to have many shortcomings. Not all of Peirce's original terms and variations are included. Furthermore, the user of the dictionary is asked to keep in mind that the quotes provided are only samples extricated from their proper context; to truly understand Peirce's point, the user should turn to the full original texts. Nonetheless, the chronological ordering of the quotations may provide some insight into Peirce's philosophical development; the dictionary entries display, in a concise space, Peirce's varying attempts at clarifying his key concepts.
     A special problem in compiling a dictionary of Peirce's terms is deciding when different words are used as synonyms and when the variations signify relevant conceptual differences. The Commens Dictionary of Peirce's Terms takes the actual word, as it is given by Peirce, as a starting point for classification. Consequently, such terms as "icon" and "likeness" are treated as separate terms, although these words evidently refer to the approximately same idea of iconicity (certain words, such as "commens" and "commind", are treated as different forms of precisely the same term, however). Admittedly, this principle can have the disadvantage of multiplying the number of entries in the dictionary, and perhaps gives the impression of greater fragmentation than necessary; but it lessens the danger that the editors' interpretations of Peirce's thought dictate the content of the dictionary to an unacceptable degree. Instead, possible synonymy and particularly important connections are indicated with links between the words.
     New terms and quotes will be added to The Commens Dictionary of Peirce's Terms. Peirce scholars and other users are encouraged to suggest additions to the dictionary. Please see the guidelines for contributors on the Contribution Form. General feedback and suggestions for improvement are also welcome.