Given the balkanized state of the field of linguistics in the twenty-first century, it may be easy to forget that an à la mode view of grammar may not necessarily be the best or truest. Apropos, a book published by Y-H-B almost a quarter of a century ago, The Sense of Grammar: Language as Semeiotic, still shows the way toward an understanding of the coherence of grammatical facts by stressing the overriding importance of diagrammatic semeiosis, wherein diagrammaticity (diagrams = icons of relation) prevails over arbitrariness.
This truth can be demonstrated concisely by examining the relation between mood and number in contrary to fact statements in English. The traditional norm requires such statements (as in wishes) to utilize the plural instead of the singular with a singular agent (“I wish I were in Dixie,” etc.). The contemporary tendency away from the plural may seem to restore grammatical coherence, but this is a specious judgment based on a basic incomprehension of how grammar makes sense semeiotically.
More precisely, the use of the plural number with the subjunctive mood constitutes a supervening coherence based on iconicity. A diagram (as noted) being an icon of relation, and the marked number being the plural (vis-à-vis the singular), just as the subjunctive mood is marked vis-à-vis the indicative, the sense of the use here of the plural transpires from the coherence of the markedness values of the two relevant grammatical categories. The Sense of Grammar may be out of print, but its purport has not suffered desuetude withal.