On the adjective considered as the limitation of an idea, a function likewise fulfilled by common and proper nouns in the English language: common errors.

Of the inexactness in considering it always a representation of the noun; what first and second person pronouns represent and what the true function of third person pronouns is: their affinity with the demonstrative; classification of pronouns and the difficulty of carrying it out without confusion.

Of the origin of the article in Greek; of how the lack of it was made up for in Latin, and proof deduced from this comparison to support the belief that the article is nothing but a demonstrative.

Particular characteristics of the participle and the infinitive. Examination of whether the substantive verb is the only verb and whether the substantive "to be" is a verb or only a relation.

Whether they should be considered necessary elements of the so-called "adjective" verbs; nature of the two participles known in English: their similarity with those of ancient and modern languages; the remarkable lack of future participles: whether they exist in Spanish and their reduction to the simple future.

Whether its only function is to qualify the verb; that it is an invariable part of speech except for degree in all languages; that it is equivalent to adjectives or to small phrases, and thus does no have to be classified or composed in any language; how others parts of speech are transformed into adverbs and how there are transformed into conjunctions, prepositions, etc.