Gradus ad Parnassum
The Latin phrase Gradus ad Parnassum means "Steps to Parnassus" (see below). It is sometimes shortened to Gradus. The name Parnassus was used to denote the loftiest part of a mountain range in central Greece, a few miles north of Delphi, of which the two summits, in Classical times, were called Tithorea and Lycoreia. In Greek mythology, one of the peaks was sacred to Apollo and the nine Muses, the inspiring deities of the arts, and the other to Dionysus. The phrase has often been used to refer to various books of instruction, or guides, in which gradual progress in literature, language instruction, music, or the arts in general, is sought.
Classics
The first application of the phrase is to a kind of Latin or Greek dictionary, in which the quantities of the vowels are marked in the words, to help beginners to understand the principles of Latin verse composition, in relation to the values of the metrical feet. The first 'step' or lesson is contained in the title phrase itself, because 'gradus' being a fourth-declension noun (a step), with a short '-us' in the singular, becomes 'gradūs', with a lengthened '-ūs', in the plural (steps). The difference in meaning teaches one to observe the difference in vowel quantity between two forms which look the same but have different grammatical properties, and so to pronounce the title of the dictionary correctly. Then 'Parnassus' is a poetic figure alluding to the Muse (of poetry): and the second function of the Thesaurus is even so, to illustrate such figures. Therefore, the whole expression Gradus ad Parnassum is not just a title but an epitome of the work itself, combining declension, construction, scansion and figure.
