Effect to Cause.  In actual events, the cause always precedes the effect, but in discussion it is sometimes better not to follow natural or usual orders.  Many explanations gain in clearness and effect by working backwards.  A voter might begin by showing the condition of a set of workmen (an effect), then trace conditions backward until he would end with a plea for the repeal of a law (the cause).  A student might explain a low mark on his report by starting with the grading (the effect) and tracing backwards all his struggles to an early absence by which he missed a necessary explanation by the teacher.  A doctor might begin a report by stating the illness of several persons with typhus; then trace preceding conditions step by step until he reached the cause—­oysters eaten by them in a hotel were kept cool by a dealer’s letting water run over them.  This water in its course had picked up the disease germs—­the cause.  Many crimes are solved by moving from effect to cause.  A lawyer in his speeches, therefore, frequently follows this method.

Both these methods are so commonly employed that the student can cite instances from many speeches he has heard or books he has read.

Time Order.  Somewhat similar to the two preceding arrangements of exposition are the next two based on time.  The first of these is the natural time order, or chronological order.  In this the details follow one another as events happened.  It is to be noted, however, that not any group of succeeding details will make a good exposition of this sort.  The parts must be closely related.  They must be not merely sequential but consequential.  Dictionary definitions will explain the difference in meaning of those two words.  This method is somewhat like the order from cause to effect, but it is adapted to other kinds of topics and other purposes of explanation.  It is excellently suited to historical material, or any related kind.  It is the device usually employed in explaining mechanical or manufacturing processes.  In mere frequency of occurrence it is doubtlessly the most common.

Time Order Reversed.  The student who starts to cast his expositions into this scheme should judge its fitness for his particular purpose at the time.  It will often become apparent upon thought that instead of the natural chronological order the exact opposite will suit better.  This—­time order reversed—­explains itself as the arrangement from the latest occurrence back through preceding events and details until the earliest time is reached.  It is quite like the arrangement from effect back to cause.  It might be used to explain the legal procedure of a state or nation, to explain treaty relations, to explain the giving up of old laws.  The movements of a man accused of crime might be explained in this way.  An alibi for a person might be built up thus.  The various versions of some popular story told over and over again through a long period of years might be explained after such a manner.