Hearers can tell from the illustrations whether a sermon is practical. The preacher's illustrations will indicate whether the preacher is kind and discriminating, or whether he lacks those qualities. Neither propositions alone nor illustrations alone can bridge the gap between generations, much less centuries. Together they make truth accessible and comprehensible. The best preaching never addresses the intellect alone or the emotions alone.
Man is both an intellectual and an emotional creature.
Illustrations that address the intellect through the emotions address the hearers as the scripture addresses them. The aim of preaching is not just to explain or define. Preaching also aims to implore hearers to believe what God said and to do what God commanded. Christianity is incarnational. Preaching should be as well.