The word 理所当然 is formed from the characters 理 (reason), 所 (that which), 当 (ought to), and 然 (thus). In this construction, 理 provides the logical basis, 所 introduces the clause, 当 expresses obligation, and 然 indicates the resultant state. Combined, they create a literal meaning of "according to reason, it should be so", directly conveying that something is natural or expected based on logical principle.