In making my commentary, I have conceived that my duty allowed me to employ a method whereby I have more than once secured this result: namely, that if my work be compared with those ancient works, it is found at times to present the old matter in a new form.  For the experience is common that, an invention once produced, additions are easily made. But to our task.

In this Fifth Book, I shall treat simply of Interchange of Power in Letters, - the second Principle Mode. As the first Mode had to do with the Order of Collection of Letters, so this next following Mode deals with Power, being descriptive of the various ways in which Power is interchanged between one letter and another.

This Interchange of Power is accomplished through Transposition of Letters. But since Interchange takes place immediately, mediately, or figuratively, so shall Transposition be called: Immediate, Mediate, or Figurative.  The first, because the Power of the letters is interchanged immediately between one letter and another: the second, because the letters are first interchanged with numbers and then the Power of the numbers is in turn expressed through letters: the last, because, to Transposition, either Mediate or Immediate, various additional features are added, whereby the Transposition is, as it were, transformed. Immediate Transposition holds the primacy: it must, therefore, be called, Primary: Mediate Transposition is Secondary; and the final method is Accessory.  To the explanation of these, as it were Universal, Modes, is devoted the whole of this Fifth Book.

The first Universal Mode is and is called Primary Transposition. This is Direct, which takes place whenever we perform Interchange by straight-forward method, without the diminution of the Transpositive alphabet, or alphabet to be written, and without the suppression of any letter of the other alphabet, Oblique, or Inverted.  Wherein these last-mentioned Methods differ from Direct Transposition has been fairly well indicated already, and the matter will again come up for mention when we come to discuss the Modes individually.