墮胎是一個非常值得研究的問題，因為墮胎是一種特殊的損害，而這種損害與一般 的損害不同。墮胎這行為有以下的幾個特點:一、行為的主客體為共同體，二、墮胎這行為的 目的或結果是墮胎客體遭受損害以至於無法存在，三、墮胎這行為在實踐上只由行為主體決 定，四、墮胎客體無法反抗，五、對於墮胎主體而言，墮胎這行為的價值是自相矛盾的。 在本文第二部分，由充足理由分析，得到以下的幾點:一、變動上，墮胎是一種與自然 相抗衡的變動，二、在認知上，任何意識的表達及意志的實踐能力皆存於墮胎主體，墮胎客 體則無，三、在存有上，墮胎客體與墮胎主體之間存在著一不可避免的矛盾，這個矛盾只來 自墮胎主體，四、在意志上，墮胎主體對自我造成的損害由於起於其意欲之自我決定，因而 墮胎主體無法自相矛盾地反對這個行為的結果。 在本文第二部分，由道德形上學分析，得到以下的幾點:一、依據Ulpian的三個公式， 無論將墮胎主體及客體之關係視為共同體或是相異者，皆可以依法之法則或公式判定墮胎行 為之不法。二、若可能的話，墮胎不應當屬於公法領城之規範，而應由私法來規範，公法是 否能加以規範成為一個開放的領域，然而其效力不應該不當地侵入私法領域，三、品德作為 一有義務的目的與格律上的強勢，墮胎不可能成為品德。

　　　　　In this articles J tried to analyze the problems of abortion fundamentally. This analysis is based upon two different methods of philosophical investigation. One is 'le principe de la raison suffissante' which had been invented by W.G. Leibniz and further developed in the subject-object-observation by A. Schoppenhauer. The other is 'Prinzipien der Metaphysik der Sitten' which can be divided into two parts, namely 'Prinzipien der Rechtlehre' and 'Prinzipien der Tugendlehre.In the way of 'le principe de la raison suffissante' I made some conclusions at the end of this article as following: 1. The abortion is a action against nature. 2. The will and its 'praxis' subsists in the subject of the abortion (namely the pregnant woman), not in the object (namely the unborn infant). 3. It exists an opposition between the abortionist and the unborn baby. 4. After self-decision to abort, the abortionist must bear the consequence contradictorily. In the second part, I acquired some viewpoints as following: 1. According to Ulpianus' three formulae the abortion must be illegal or not legitimate. 2. If possible, the abortion will not be legislated in public law. But if it can be legislated in public law, it must not injure private right. 3. Categorically the abortion is not one of the virtues because the virtue is the strength of obligatory end and maxim.