 Although Fârâbî does not make explicit connections between the different Parts of the Book of Letters, Part II can be seen as giving an implicit program for Parts I and III, each of which is organized lexically around a list of terms: in each case Fârâbî lists the different meanings of the term, starting with an ordinary-language meaning and then explaining how it is metaphorically extended to a series of further meanings, including technical meanings in the different arts and especially in philosophy. Part I treats in this way terms including the names of many of the ten Aristotelian categories, or the interrogative particles from which names of categories are derived (“kamiyya” = quantity is derived from “kam?” = “how much?”, and so on); it also discusses particles such as “from” and “because” and nouns such as “being”, “essence”, and “accident”, with a heavy overlap with the list of terms investigated in Aristotle’s Metaphysics V. Part Three applies the same lexical method to the four kinds of scientific question or investigation described in Posterior Analytics II, the questions “whether X is”, “what X is”, “that S is P”, and “why S is P”. In each of these cases Fârâbî distinguishes the ways of investigating these questions in different disciplines—for instance, how they are investigated in dialectic vs. how they are investigated in demonstrative science—as if they turned on different meanings that the particles, “whether” or “what” or “that” or “why”, have in different syllogistic arts. There are clear connections between Parts I and III, notably between Part I on the senses of “being” [mawjûd] and Part III on the senses of “whether it is” [hal mawjûd]. Fârâbî evidently thinks that people have gone wrong in the sciences through confusing different meanings of the terms he discusses, in particular through confusing ordinary-language meanings of these terms with technical meanings in the syllogistic arts, or confusing meanings in one syllogistic art with meanings in another. And he thinks these problems are made worse when the technical terms of these arts are first developed in one language (Greek) and then translated into another (Arabic) in the ways he has described in Part II: if a word which has a meaning in ordinary Arabic (or in the technical vocabulary of some native Arabic art), or a word morphologically derived from such an Arabic word, has its meaning extended to serve as the artificial Arabic equivalent of some Greek technical term, then there is a serious risk that it will be misunderstood by Arabic readers. This explains why Fârâbî thinks that the sort of work Aristotle does in Metaphysics V, distinguishing different meanings of a series of technical terms, would be even more necessary in Arabic than it was in Greek.