本文從一個美國財產法的法理論──「邊界原則」，來探討我國物權法中的相鄰關係，以及專利法中的均等論，指出此二種法律原則雖然權利歸屬的方向看似相反，但蘊含相同的原理，亦即基於衡平考量而作外部成本或外部效益的分配，亦即二者都是將零碎化的財產重新整併的規則。本文以Michael A. Heller的財產零碎化理論，以及Frank I. Michelman的私有財產效率論證，作為理論的基礎。Heller認為財產法中早已存在的邊界原則，目的在防止財產因過度切割而造成不能有效率利用。Michelman的私有財產組成規則中，內部化規則與不干預規則分別作為財產權的合併與分割的規則，是Heller的反零碎化理論的源起。本文主張，物權法中的越界建築，以及專利法中的均等論，均為Heller所描述的邊界原則及Michelman所描述的內部化規則的例子。 越界建築中的土地購買請求權，為典型的內部化規則；基於內部化而整併權利，於法律論理上常顯示為衡平法的運作，而不干預原則常顯示為法律的形式推理。但物權法亦有不保存越界建築之效益，以及容許零碎化之情況，顯示經濟分析之推理，與法律的權利配置，二者並非完全一致。 越界行為，即行為人的行為對他人產生外部性，此外部性可能為成本，亦可能為效益。在專利均等論，則是關於申請專利範圍之外的效益的分配。美國法院以案例法方式形成均等論，亦即將發明的外部效益全部分配給專利權人，此種內部化規則造成權利過份整併，在歷史上為美國聯邦最高法院與聯邦巡迴上訴法院的少數意見所反對。直到法院也發展出均等論限制原則，才用迂迴的方式將部分的效益重新歸類為外部效益，避免權利的完全整併。我國法院對均等論的存立基礎罕見發表意見，似為有缺憾之處。

This article uses an American property theory—the boundary principle—to discuss the neighboring relations in Taiwan’s property law and the doctrine of equivalents in patent law. The aim is to point out that although these two branches of legal doctrines seemingly head toward the opposite directions concerning the distribution of rights, they both base on a similarly principle: to distribute positive or negative externalities in accordance with equitable con-siderations; both doctrines are anti-fragmentation principles aiming at recom-posing fragmented property rights. The theory of this article is founded on Michael A. Heller’s theory of an-ti-fragmentation and Frank I. Michelman’s arguments related to the efficiency of private property. Heller argues that the boundary principle long existing in property law is to prevent waste of resources caused by fragmentation. Michelman’s internalization and nonintervention rules, two composing princi-ples for an efficient private property regime, are the origin of Heller’s anti-fragmentation theory. This article asserts that the rules regarding building en-croachment and the doctrine of equivalents in patent law are the examples of Heller’s boundary principle and Michelman’s internalization principle. In the relation of building encroachment, the right to request land pur-chase by the trespasser is a typical internalization rule. To consolidate rights based on the reason of internalization often realizes in law as the operation of equity, and nonintervention rules appear as the formalistic reasoning of the law. Yet the fact that the law leaves ample possibility of unconsolidated frag-ments shows the disparity between the economic and the legal rationale. An act of encroachment is one that causes positive or negative externali-ties on another. The doctrine of equivalents in patent law is a set of rules that distributes the benefits beyond the literal scope of a patent claim. Formed by case law, the doctrine of equivalents used to distribute the whole external ben-efits to the patentee; this kind of internalization rule caused too much consoli-dation of the rights and was opposed by the dissenters at the U.S. Supreme Court and the Court of Appeals for the Federal Circuit. The development of the limiting rules of the doctrine of equivalents allows the courts to distribute some of the benefits beyond the literal scope of a claim to competitors by re-categorizing them as externalities; the limitation rules thus avoid complete consolidation of rights. By contrast, it seems a pity that Taiwan’s courts rarely comment on the legitimation basis of the doctrine of equivalents.