The semicolon, long in decline, may be in renewal, but it remains rare in its central use: replacing a comma and coordinating conjunction to unite two independent clauses. Current pedagogy tells us that the semicolon represents a bigger break than the conjunction and a smaller break than period. Could this account have caused the semicolon's decline, as we increasingly relied on written accounts for rules of mechanics? Can writers really classify the degree of logical connection of clauses into as many as three distinct categories? Most people have a hard enough time with only two. Plain-language exponents of short sentences instruct to break off a sentence when it becomes "too" long. Does anyone expect ordinary people or even skilled writers to divide degree of connection between connected thoughts into three neat, objective compartments? Even if the compartments existed in an objective sense, our mental powers may be too weak to distinguish them.
Guided by finding an interval greater than a comma but less than a period, writers reasonably choose not to apply voluntarily an intermediate standard as ephemeral as clear-and-convincing evidence, a standard so unintuitive people apply it only when serving on a jury under court order. If the semicolon had vitality before people relied so heavily on formal explication, people must have used a different criterion, either in addition to or in place of the intermediate-pause account. The real vitality of the semicolon — the best way to use it — depends on the need for a neutral connector rather than an intermediate pause because to show a connection between ideas facially we rely primarily on two coordinating conjunctions, but and and. But combines logical conjunction with contrariety. When you encounter but, the writer implies that hearing the first clause would ordinarily decrease your expectation of hearing the second. It seems natural to assume equivalence between and and logical conjunction: but stripped of its contrariety. So assumed, and is the generic connector, but the negative-expectation connector, and no positive-expectation connector exists. And may not be quite as positive as but is negative, but and is positive, not generic. Otherwise we would have to choose more carefully between and and but whenever but applies.
The semicolon is the language's neutral connector. Use it to connect ideas directly without implying either positive or negative expectation of what follows.
(Next entry I'll discuss the main circumstance in which expectation neutrality is important.)