本文詳細檢視了主體（subiectum）與客體（obiectum）這一對概念，如何被現代法國（Pothier、Demolombe）、德國（Hugo、Thibaut、Savigny、Puchta、Windscheid）以及葡萄牙與澳門（Guilherme Moreira、Manuel de Andrade）法學所繼受，並最終在法國民法典、德國民法典、葡萄牙民法典與澳門民法典中被採納。有別於哲學上另有新出路（Kant），主客概念在法學上卻遇上了發展困境，因為主體完全等同於人，故似有若無，而客體的內涵（intension）又非常空洞，因而外延（extension）非常寬廣，而且極度歧義。因此，這場從「人物對立」到「主體客體對立」的範式轉換（paradigm shift）不算太成功。最後，本文嘗試梳理亂狀，尤其是將客體分為如下多階客體，予以重構：法律行為（Rechtsgeschäft；negócio jurídico） → 法律效果（＝法律行為客體或稱法律行為標的） → 權利義務 → 行為或稱舉動（Handlung；acto）亦即作為或不作為（＝直接權利客體） → 物（＝或有的間接權利客體）。

This paper examines how the “Subject-Object Dualism” (“SOD”) was inherited by the French (Pothier and Demolombe), German (Hugo, Thibaut, Savigny, Puchta and Windscheid) and Portuguese (Macau) jurists (Guilherme Moreira and Manuel de Andrade) and Civil Codes (Code Civil, BGB, Código Civil Português and Código Civil de Macau). But while the “SOD” has a new path in Philosophy (Kant), its development in Law encounters difficulties, because subject is in fact totally equivalent to person, which makes it seem dispensable. Moreover, the intension of object is highly vague, which leads to extremely large extension and semantic ambiguity. Therefore, this paradigm shift from “Person-Thing Dualism” to “SOD” is less successful. Last but not least, this paper also tries to give a solution to such disorder, especially by classifying the concept object into different levels: Rechtsgeschäft (negócio jurídico) → Rechtsfolge (legal effect) (= Object of Rechtsgeschäft) → Right and Obligation → Act (Handlung; acto) i.e. facere or non facere (= Direct Object of Right) → Thing (if any) (= Indirect Object of Right).