itself being built up from isolated signs; and (B) he could discover grammatical facts through syntagmatic and paradigmatic analyses. Syntagmatic and paradigmatic relations Language works through relations of difference, then, which place signs in opposition to one another. Saussure asserted that there are only two types of relations: syntagmatic and paradigmatic. The latter is associative, and clusters signs together in the mind, producing sets: sat, mat, cat, bat, for example, or thought, think, thinking, thinker. Sets always involve a similarity, but difference is a prerequisite, otherwise none of the items would be distinguishable from one another: this would result in there being a single item, which could not constitute a set on its own. These two forms of relation open linguistics up to phonology, morphology, syntax and semantics. Take morphology, for example. The signs cat and cats are associated in the mind, producing an abstract paradigm of the word forms of cat. Comparing this with other paradigms of word forms, we can note that in the English language the plural often consists of little more than adding an s to the end of the word. Likewise, in syntax, through paradigmatic and syntagmatic analysis, we can discover the grammatical rules for constructing sentences: the meaning of je dois ("I should") and dois je? ("Should I?") differ completely simply because of word order, allowing us to note that to ask a question in French, you only have to invert the word order. A third valuation of language stems from its social contract, or its accepted use in culture as a tool between two humans. Since syntagmas can belong to speech, the linguist must identify how often they are used before he can be assured that they belong to the language. Synchronic and diachronic axes To consider a language synchronically is to study it "as a complete system at a given point in time," a perspective he calls the AB axis. By contrast, a diachronic analysis considers the language "in its historical development" (the CD axis). Saussure argues that we should be concerned not only with the CD axis, which was the focus of attention in his day, but also with the AB axis because, he says, language is "a system of pure values which are determined by nothing except the momentary arrangements of its terms". To illustrate this, Saussure uses a chess metaphor. We could study the game diachronically (how the rules