Methodology: Coherence and cohesion

Very briefly: A text is cohesive if its elements are linked together. A text is coherent if it makes sense.  It should be clear that these are not the same thing. That is, a text may be cohesive (i.e. linked together), but incoherent (i.e. meaningless). Here is one such (invented) text:

Each sentence is notionally linked to the one that precedes it, using both lexical and grammatical means, but the text is ultimately senseless - to me anyway (and I wrote it!).

The following (much quoted) exchange, however, is coherent to most people, even though there are no obvious links between its parts:

It is coherent because we can easily imagine a context in which it would make sense. Just as (albeit with more ingenuity perhaps) we can imagine a context in which the following would make sense:

Put simply, then: cohesion is a formal feature of texts (it gives them their texture), while coherence is "in the eye of the beholder" - that is to say, it is the extent to which the reader (or listener) is able to infer the writer's (or speaker's) communicative intentions. Thus, cohesion is objectively verifiable, while coherence is more subjective. A text may be coherent to you, but incoherent to me.

The exact relationship between cohesion and coherence is a matter of contention, however. While it is true that a sequence of unlinked utterances can make sense, it is often the case that some form of linking, e.g. with cohesive devices such as and, but, so, can make it easier for the reader (or listener) to process and to make sense of what they read (or hear).  Nevertheless, a text which is basically poorly organised is not going to be made more coherent simply by peppering it with moreover, however and notwithstanding. The following text (devised by the writer on writing, Ann Raimes) is an example of a text that is "over-egged" with cohesive markers, and which is typical of the kind of texts that many students produce as a result of an over-emphasis on linking devices at the expense of other ways of making texts cohesive (of which probably the most important is lexis):

So, to return to the second part of the question, what are some practical ways to teach cohesion and coherence?

The way that textual cohesion is achieved is best learned through paying close attention to the way sentences are linked in texts. There are a variety of cohesive devices, both lexical and grammatical, of which linkers (and, so ,but) are just one. (For a comprehensive list, see the entry under cohesion in An A-Z of ELT, Macmillan, 2006). Cutting (short) texts up and asking learners to order them is a good way of drawing attention to the way that they are linked. I am fond of using short articles from children's encyclopedias.  Identifying lexical chains in texts - that is, repetitions, the use of synonyms and hyponyms, and words from the same lexical field - is also a useful way of alerting learners to the key role that lexis has in binding a text together.

Coherence is more elusive but it has a lot to do with the way that the propositional content of texts is organised. If the content of a (written) text is organised in such a way that it fulfills the reader's expectations, it is more likely to achieve its communicative effect. This means that learners can be helped to write coherent texts through the analysis of the generic features of particular text types. This has long been the approach to teaching business, technical, and academic writing.  More important still, is second-guessing the intended reader's questions, and then answering them. This means that it is important that, when doing writing tasks, students have a clear idea both of the purpose of the text, and of the intended readership. Good writers are able to "keep their reader in mind". Keeping your reader in mind does not guarantee coherence, but it would seem to be a prerequisite.  (For more ideas on how to teach both cohesion and coherence, see Chapters 2 and 3 of Beyond the Sentence, Macmillan, 2005).