Certain general rules may be stated and should be learned.

Many cases, however, will arise in which the rules will be differently interpreted and differently applied by different people.
The comma is the least degree of separation possible of indication in print.

Its business is to define the particles and minor clauses of a sentence.

A progressive tendency may be seen in the printing of English for centuries toward the elimination of commas, and the substitution of the comma for the semicolon and of the semicolon for the colon.

Compare a page of the King James version of the Bible, especially in one of its earlier printings, with a page of serious discourse of to-day and the effects of the tendency will be easily seen.