Cohesion and Coherence
Writing is cohesive when one sentence sticks to the next and one paragraph sticks to the next.
The known-new contract helps achieve cohesiveness. We read non-fiction prose, especially
dense and technical prose, with an unconscious expectation that the writer will slowly build our
knowledge about their topic. Sentences interest and make sense to us when they contain both
known and new information, and when the known precedes the new. Often, when we find a text
confusing, the writer hasn’t followed this known-new contract with the reader.
Writing is coherent when all of the sentences in a paragraph, while slowly unfolding new
information, do so around a single topic or idea.1
High levels of various metals give coal combustion residuals (CCRs) the
potential to have serious health implications for the environment as well as
humans or other organisms that come into contact with these pollutants. Various
animals (known) that were observed breeding near these coal ash ponds have
shown significant heavy metal accumulation (new) in their tissues. Heavy metal
accumulation (known) will likely lead to behavioral, physiological, and
developmental abnormalities (new) in these animals (Chatterjee 2009).
Deformities in fish (known), including an extended lower jaw and spinal
curvature, have also been noted in bodies of water (new) near settling ponds due
to elevated metal concentrations (Ruhl et al. 2012). Additionally, ground and
surface water contamination (known) with these metals could potentially lead to
human health consequences (new/also returns to main idea of paragraph).
In this example, note how each new sentence sticks to the previous sentence through repetition of
the known. And the whole paragraph still coheres around a single main idea: the health
consequences of metal contamination from CCRs.
1 Joseph Williams and Gregory Colomb. Style: The Basics of Clarity and Grace. Boston: Longman, 2012.