In revising Tertium Organum for the second edition in English my chief concern has been to coordinate its terminology with the more developed terminology of those of my books written after the publication of the second Russian edition of Tertium Organum, from which the English translation was made. Such a unity of terminology is the more necessary because I am obliged to lead the reader into regions of thought and knowledge where boundaries have not been clearly established, and where different authors - and often one and the same author, in different works and during different periods of his activity - have called the same thing by different names, or different things by the same name. It must be admitted that language is a weak and inadequate vehicle even for the expression of our usual understanding of things, to say nothing of those moments when the understanding unexpectedly expands and becomes deeper, and we see revealed an entire series of facts and relations for the description of which we have neither words nor expressions. But quite aside from this, in ordinary conditions of thinking and feeling, we are frequently at a loss for words, and we use one word at different times to describe different things. On the other hand, it is no merit in an author to invent new words, or to use old words in new meanings which have nothing in common with the accepted ones - to create, in other words, a special terminology. I have always considered that it is necessary to write in the language which men commonly speak, and I have endeavored to do this, although in some cases it has been necessary to make some additions to and corrections of that language for the sake of exactness and lucidity. In due time I shall separately consider the subject of language and the methods of its adaptation for the transmission of exact thought. For the present I have reference only to the language of Tertium Organum. The first word demanding a more careful use is "consciousness." In conversational language and in everyday psychology, even in psychology purporting to be scientific, the word consciousness is often used as a term for the designation of a complex of all psychic functions in general, or for their separate manifestations. At present I have not access to the necessary books - I abandoned them all in Petrograd, four years ago - but to the best of my recollection Prof. William James defined thought as "a moment of consciousness." From my standpoint, which I shall elucidate in works now being prepared for the press, it is necessary to regard consciousness as distinct from the commonly understood psychic functions: thought, feeling and sensation. Over and above all this, consciousness has several exactly definable forms or phases, in each one of which thoughts, feelings and sensations can function, giving in each different results. Thus consciousness (be it this or something other) is a background upon which thoughts, feelings and sensations reveal themselves. This background can be more or less bright. But as thoughts, feelings and sensations have their own separate life, and can be regarded independently of this background, so can it be regarded and studied independently of them. For the present I shall not insist too strongly upon the idea of this ground as something separate in its substance from psychic functions. The practical result is the same if we say that thoughts, feelings and sensations may have a different character, and that thoughts, feelings and sensations of this or that character create this or that state of consciousness. This translation, made without my knowledge and participation, at a time when I was cut off by war and revolution from the civilized world, transmits my thought so exactly that after a very attentive review of the book I could find only one word to correct.