民法第188條第1項「因執行職務」之認定係近來重要之實務問題，惟學說與實務對其認定基準難有共識。實則，處理本條項之「涵攝」問題時，應同時重視事實面邏輯推理之正確性以及法價值面評斷之妥當性。本文藉由形式邏輯歸納出受僱人之侵害行為與其執行職務行為間至少應具備下列關係之一時，方可能符合「因執行職務」要件而將執行職務納入損害發生之因果歷程中，作為課予僱用人本條項責任之前提：（1）侵害行為係執行職務自體之行為；（2）執行職務行為係侵害行為之充分條件或必要條件者；（3）侵害行為由職務上之行為與無關職務行為所連言、或選言者。對照以最高法院42年台上字第1224號民事判例所揭櫫之「執行職務自體之行為」、「執行該職務所必要之行為」以及「客觀上足認為與其執行職務有關之行為」三判斷基準，恰分別符合此揭命題之邏輯基礎；至於「職務上予以機會之行為」、「與執行職務之時間或處所有密切關係之行為」、「行為外觀」或「個人之犯罪行為」等基準，則欠缺邏輯性。

The employer is jointly liable to compensate for any damage which the employee, due to the discharge of his appointed duty, unlawfully causes to third parties as provided in Civil Code § 188(1). The rational prerequisite for this vicarious liability of employers according to the principle of ”corrective justice” stands that there must be a rational linkage between the discharge of appointed duty, the wrongdoing of the employee and consequently the harm caused.However the linkage criteria varied and caused disputes, to which legal theorists and even learned judges have devoted themselves in the heavily piled literatures trying very delicately to frame practically sound principles only to achieve very limited success. The possible defect of the foregoing approaches herein lies in their inobservance of the causation element intrinsic to Civil Code § 188(1), i.e. as the wording ”due to” represents.This article, by means of reviewing the related holdings of our supreme court and applying the reasoning technique of formal logics, attempted to elaborate the criteria of this linkage prerequisite with special emphasis on the logical causation between the discharge of appointed duty and the wrongdoing of the employee. We, with reference to Supreme Court Precedents Year 42-No.1224 (1953), therefore concluded that linkage in question exists if the wrongdoing of the employee is actually the discharge of duty itself, the wrongdoing is the essential or necessary condition of the discharge of duty, or the wrongdoing comprises both or either only one of the discharge of duty and other doing outside the scope of employment. In any of the above, there accordingly will be a direct, conjunction-or disjunction-causation linkage established between the discharge of appointed duty and the harm caused, which build up the logic rationale for vicarious liability of the employers. Hopefully this article will help to elucidate the logic rationale of ”due to discharging appointed duty” as provided in Civil Code § 188(1), and set up a clear-cut criteria to settle the dispute therein.