Coherence and logic
A sense of coherence and logical progression is achieved in a text by making clear links between sections, clear links between paragraphs and clear links between sentences within each paragraph. To create clear links, and maintain the right focus in each section and paragraph, you need to consciously control how paragraphs and sentences begin, and how they indicate to the reader the coming point or topic. First position in a text, a paragraph, and in each sentence, indicates to the reader what the coming message is about.
Sections
Headings and numberings are the signposts and introductions to each chunk of information you present. In naming and numbering sections and sub-sections within your thesis, you smooth the flow of information, and show the reader a logical connection between different sections. In a thesis on the behavioural ecology of yellow-bellied gliders, for example, each chapter reported on a separate aspect of behaviour, and each was structured as a mini thesis. The informational content of the sections is indicated in the headings, and the hierarchical relationships between sections is clear from the numbering system:
- 2.3 Results 15
- 2.3.1 Eucalypt Sap 15
- 2.3.2 Honeydew 15
- 2.3.3 Arthropods 16
- 2.3.4 Manna 17
- 2.3.5 Nectar 17
- 2.3.6 Overall Diet 18
- 2.3.7 Food Availability Indices 19
- 2.4 Discussion 20
- 2.4.1 Diet of Exudate-Feeding Aboreal Marsupials 20
- 2.4.2 Eucalypt Sap 21
- 2.4.3 Honeydew 15
- 2.4.4 Arthropods 16
Paragraphs
Effective paragraphs are tightly structured packages of information on a single topic or point. They each need an appropriate topic sentence - that is, the first sentence needs to accurately indicate what the paragraph is actually about. If the topic or point of a particular paragraph is complex, then the first sentence should contain a complex noun group that accurately and concisely reflects all the things to be discussed. Consider the difference between the following versions of the same information, and how changing the starting point signals to the reader a slightly different overall point for the coming paragraph:
Comment: this opening indicates that the paragraph will be about the 'aqueous phase'. The active verbs indicate that a process is being recounted rather than defined here. If the writer actually goes on to present other kinds of information through the paragraph, then this is a poor beginning. The paragraph should remain focused on the topic initially introduced.
Amino acids are diffused and removed from fossils by an aqueous phase. This is a long and slow process...
Comment: this opening indicates that the paragraph will be about 'amino acids'. The verbs signal a recount or explanation of processes, rather than a discussion of concepts.
The diffusion and removal of amino acids from fossils by an aqueous phase is a long slow process...
Comment: the writer indicates here that the coming paragraph is about a complex set of concepts and processes, which will presumably then be explained and elaborated. If all these things are actually discussed in the paragraph, then this is an effective introduction to the paragraph.
Once you have drafted your text (decided what information you want to present), you need to ensure that it will be clear to a reader what the point and purpose of each new paragraph is. This indication should be up front and immediate, not buried in the middle of the paragraph. You always have choice when it comes to wording your messages - you can change which element you begin with. Sometimes it works to lead up to the main point of a discussion paragraph, and put that 'point' at the end. Usually, it does help the reader follow and quickly digest your material if you put the point up front. What matters most though is that each paragraph consist of a number of sentences which extend, explain, illustrate and contextualise one main point or topic. Consider the example about gliders:
To counteract the lack of protein in eucalypt sap, honeydew and manna (Basden, 1965, 1966; Patoll 1982; Stewart et al. 1973), yellow-bellied gliders harvest arthropods or pollen to meet their protein requirements.
At Bombala, gliders harvest arthropods principally by peeling back loose, shedding bark or by searching through hanging bark ribbons which persist on the trunk and branches of E. viminalis. This loose bark, shed from the smooth trunks and branches of eucalypts, is an important substrate, rich in arthropods and associated carbohydrates (i.e. insect honeydew), (Recher et al. 1983, 1985, Henry & Craig 1984, Goldingay pers.obs., Kavanagh 1987b). In the present study, it accounted for 23% of the total feeding observation time. The value of this resource may be greater during winter as many arthropods, in particular coleoptera, overwinter under bark (Smith 1982a, Recher et al. 1983, pers. Obs.); however its usefulness is determined by the bark-shedding pattern of the different tree species. In the present study there were always some species which had loose bark present (with attendant arthropod fauna) with different species tending to have staggered patterns of bark shed (see also Kavanagh 1987a). Eucalyptus viminalis displayed a more synchronised bark shed than any other species and appears to provide a very abundant resource.
Comment: These sentences expand on the idea presented in the topic sentence.
To check that your text has a logical and coherent flow within each section, look closely at each paragraph, and the topic sentence of each. There should be some indication in the repetition of words (or use of synonyms and related words) that the various messages are all about related things. Consider this example to guide you:
When a dam core leaks as a result of a crack, erosion of the leakage channel walls occurs. The eroded material breaks down into fine constituents and these particles are transported via fluid flow towards the filter. Impervious cores, comprised of non-dispersive soils, may generate fine particles in a flocculated state depending on the salinity of the reservoir water and the mineralogy of the soil. An effective filter must take the size of the flocculated particle into consideration: pore channels must be sufficiently fine to trap the particles requiring protection, and sufficiently coarse to facilitate the passage of water through the filter.
To assist in the design of effective granular filters for dam cores, more needs to be understood about the interaction of base and filter particles at the base-filter interface. Laboratory tests that simulate this region of the filter could provide information about the infiltration of finer base particles into the filter voids. The formation of a self-filtration zone in this region is indicative of the ability of a filter to retain a stable layer of base particles, and in effect, arrest cracking; thus, a more precise understanding of the formation of self-filtration zones within this region may lead to more effective filters and safer dams.
Sentences
Coherent and logical movement from one sentence to another within a paragraph can be similarly maximised by controlling which bits of information are presented first within each sentence. Sometimes a small reorganisation of sentence content can make a major difference to the readability of a text. It usually makes most sense to begin with known information and move onto the new information within a sentence, because if the connections between messages aren't immediately clear, the reader can lose the thread of the discussion. If a reader feels they have to work hard to make sense of your text, they might not want to bother - especially if they are tired.
Comment: Notice how the information flow in this paragraph is smooth and logical. Information presented in one sentence as 'new' (at the end) is presented in a subsequent sentence as 'given' or known (at the beginning of the sentence).
Transitions
Once it is clear what each paragraph is really about, and checked their internal organisation, you can check that the links between paragraphs are clear. Transitions between paragraphs and sections need to be checked carefully to ensure the reader is constantly being reminded where they have been and where they are being taken, and how the various bits of information are connected.
http://ccc.commnet.edu/sensen/part3/sixteen/techniques_transitional.html
http://ccc.commnet.edu/grammar/transitions.htm
See UniLearning for further guidance on logical writing.
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