one's cherished opinion; one's pet theory
Refers to a personal opinion or theory that one holds firmly, often with a nuance of attachment or stubbornness. Used in formal or written contexts.
He never budges from his cherished opinion.
その学者は持説を発表した。
The scholar presented his pet theory.
Compound of 持 (ji, 'hold') and 説 (setsu, 'opinion, theory'). The exact historical derivation is uncertain, but the meaning follows naturally from the components.