opinion, theory, explanation, rumor
説 centers on expressing ideas through words: an opinion, a theory, an explanation, or even a rumor—all are ways of putting thoughts into speech.
説 combines 言 (speech) with 兑, which likely contributes the sound and originally meant 'to exchange' or 'to pass through,' giving the idea of exchanging words or explaining.
Words (言) are exchanged (兑) to share an opinion, theory, or explanation. Picture two people talking, their words flowing back and forth like a conversation.
For セツ, imagine a set of theories being explained: set -> セツ, and each theory is a set of ideas expressed in words.
explanation; exposition; description; account; caption; legend
novel; story; (work of) fiction
explanation; commentary; exposition; elucidation
legend; folklore; tradition
theory; doctrine
persuasion
speech; address
sermon; preaching; homily
hypothesis; supposition; assumption; tentative theory
to explain; to preach; to advocate
editorial; leading article; leader
established theory; accepted opinion; accepted explanation
article; discourse; dissertation; (written) argument; commentary
emphasizing (a point, argument, etc.); stressing; insistence; arguing strongly (for, against)
theory
paradox
election tour; election campaign; stumping
introduction
novelist; fiction writer
mystery novel; detective novel; whodunit
persuasiveness; powers of persuasion; cogency
(printed) instructions; manual; explanatory leaflet (pamphlet, note); description