In classifying sermons according to structure Sangster is trying to steer between the twin evils of mindless meandering and Spiritless rigidity. The perils of both are clear. A sermon prepared without thought as to progress and purpose will move from point to point leaving the hearers confused or bored. A sermon prepared according to a presupposed structure will often break the subject matter into an unnatural format which detracts rather than enhances the flow of the message. Sangster principally tries to address both errors by making the reader aware of the different types of structure which are possible. As when classifying by content he acknowledges that one structure may exist within another and that new structures are possible. However he asserts that preaching for the 'long haul' requires a good blend of structures to prevent monotony and that the avoidance of same is usually due to complacency or laziness. The five structural types he identifies are Exposition, Argument, Faceting, Categorizing and Analogy. Again the bulk of the chapter, and this paper, are given over to an explanation of the five types.
By far the largest classification in Sangster's taxonomy, with seven sub-types, is Exposition. The broad expanse of this class is explained by the fact that he classifies anything involving explanation of something that exists as being exposition. He notes that it is more normal to leave the term exposition more narrowly defined as explanation of Bible passages but he considers that definition to be too narrow. In general Sangster concedes that the structure of these messages requires relatively little thought as the material itself generally defines the structure. The seven sub-types of exposition he defines are:
For Sangster the argumentative sermon is not necessarily one which is contentious but rather one where the rules of logic are used to make a point which is not directly and clearly stated in Scripture. The premise here is that if a truth is not directly and plainly stated in Scripture and yet some number of verses can be combined in such a way as to declare a particular truth then an argumentative sermon may be produced to show that truth. There are two logical principles that undergird this approach: deduction and induction.
Deduction may loosely be viewed as the combination of a universal truth and another truth to produce a more applied form of truth. An example might be 'all have sinned' and 'the wages of sin is death' from which one may deduce that 'all are destined for death'. Using deduction one does not produce any new truth; rather one is simply uncovering the facts which were implied by what was previously known. A deductive sermon would thus be one in which the 'newly revealed' truth was announced as a thesis and then the underlying logic was displayed to convince the hearer of the validity of the thesis.
Induction may loosely be viewed as the combination of a set of applied truths and the inference from a large enough set of applications that some general truth applies. As a somewhat silly example one could read all of the cases in the Bible where someone dies and then infer that 'all die'. As well as the potential logical value of induction Sangster views it as motivational; if a truth can be seen to have worked for many people then it may well work for me! This form of preaching is particularly apposite in a denomination where the teachings and behaviors of church fathers and denominational founders are considered proscriptive. Thus Sangster cites a typical argument that Augustine, Luther and Wesley all believed X and therefore so can we.
Sangster defines faceting as "cutting 'faces' on a gem of truth to release both its whiteness and its gleaming wonder." Somewhat less poetically one may consider it as viewing a single truth from multiple angles. Thus we might consider multiple origins of a particular issue, multiple consequences of a truth, multiple implications of a truth or multiple concrete instances of a truth. Under faceting he also places 'How to' sermons; those that do not simply exhort the believer to exhibit some behavior but which also give clear direction regarding how to do so.
It is interesting that in all of his examples Sangster alliterates or creates some other obvious connection between his headings; and yet he also cautions against doing so. His position is that whilst it is good to make the titles memorable in that way it should only be done where it falls naturally out of the subject matter. He also urges strongly that if one is faceting then it is important to keep in mind that that is what one is doing. Thus if you have three facets it would be inappropriate for two to be faceted by origin and two by consequence. Additionally he notes that all preaching must progress and that as faceting is naturally fragmented one must progress in the unveiling of the truth that the faceting is directed towards.
Categorization will probably appear too many as if it were faceting but the concept different; it is the division of a sermon based upon the classification of some object. Thus one could tackle a gospel message by delineating how it applies to the old, the middle aged or the young. A social sermon could be classified into how it applies to the different social classes. A truth could be applied individually, to a small group or globally or to different elements of the human psyche. Sangster suggests that the latter is a particularly good way of delving into the deeper emotional consequences of manner truths. Another major heading given under categorization is that of the progression of time; this is not however a narrative of events that took place over time. Rather this is a narrative of how a given truth has been taught over time; by Paul, Augustine, Luther and Wesley. Obviously this approach is less valid for those that work Sola Scriptura. As with faceting this structure leads itself naturally to the Introduction / Independent list of sections / Conclusion methodology.
The final category given is analogy and Sangster finds divine sanction for it in the Lord's use of parables. This is a sermon type in which a given picture is found and the various elements of it are used to bring out a collection of truths. Some sermon titles suggested are 'Life as a Voyage', 'Life as a Cricket Match' and 'The Devil as a bowler.' Sangster concedes that this form of sermon can easily get out of hand and draw the analogy too far and that it can be overused. Nonetheless it is clearly a graphic and winsome way to draw some into the truth.
Sangster's underlying premise is clearly sound; that if a preacher meanders he will lose the audience and that if he follows a preconceived pattern he will break his message. He then details five categories of sermon structure. The first is Exposition which he breaks into seven categories driven principally by the quantity of material covered and the method of material selection. The second is argument; the use of logical deduction or induction to produce or substantiate a truth which would otherwise not be clear from the text. The third is faceting; the viewing of a truth from multiple angles. The fourth is categorization; the division of a sermon by the classification of some object outside of the primary truth. The fifth is analogy; the use of some external well understood object as the framework upon which to hang a message. For me personally I think these distinctions are useful although I am inclined to agree with Dr Wiersbe that if you have skeletons in the pulpit you will end with cadavers in the pews.