所謂「雙重效應原則」，經常被用來解釋導致嚴重傷害的行為在道德上的允許性。道德上不允許以惡的方法(手段)來達成即便是善的目的，但若該傷害(惡)不可避免的只是為善(之可預見的)的副作用，則是允許的。
根據雙重效應原則，允許將某些良好意圖的行為所造成的傷害結果視為副作用(或「雙重效應」)，即便此成善所造成的傷害在被當成「手段」是不被允許的。【牛津哲學百科】
The doctrine of double effect is often invoked to explain the permissibility of an action that causes a serious harm as a side effect of promoting some good end. According to the principle of double effect, sometimes it is permissible to cause a harm as a side effect (or “double effect”) of bringing about a good result even though it would not be permissible to cause such a harm as a means to bringing about the same good end.
「雙重效應原則」可以引用使徒保羅的話能簡明做出此原則的揭示：我們不可以「作惡以成善」（羅馬書三8）。這個原則可從。意思是說，即使是善的目的，也不可以將惡的手段合理化。然而，假若行為所引起的惡，不是達成目的的手段，而只是該行為為達到善的目的所引發的「副作用」而已；這樣就可以不違背「雙重效應原則」，而能在道德上得到合理化，而得以免於不道德的罪名。這是傳統基督教神學中，一個非常著名的道德立場，稱為「雙重效果說」。 雙重效果說主張：任何刻意造成無辜者死亡的行動，無論可以帶來多大的好處，包括拯救大量生命，都是道德上不容許的。
「雙重效應原則」的是要解決產生在某種道德抉擇的矛盾，這些矛盾的情況中，無論我們採取何種行為，做什麼樣的決定，都會引起某種傷害或邪惡（evil）。雙重效應原則正是提出方法來，在道德上評估(to justify)某些可能引起邪惡的好行為。此處所謂「惡」是指會造成傷害或被為不道德的行為。在某些時候，這些會帶來惡的行為，雖然是必要的行為，但仍有必要經過道德上的合理化工作（moral justification），才可以付諸應用和實行。【雙重效應倫理原則及其修正理論 — 相稱論】
在道德上的評估的過程中可發現：惡的行為結果跟我們所要達成的善，有著密切的關聯。而雙重效果說並不反對行動造成嚴重的傷害後果；但認為必須考慮其與「意圖」之間的關係。根據雙重效應原則，若行為所造成的惡，是我們所要達成的善之「手段」，那麼這種行為就不能在道德上得到合理化。若所造成的惡，僅為不可避免(或可預見)的「副作用」時，則能為道德所允許。
「雙效說」指的是，即使有可預見的壞後果，如果行為是以好後果為目的，則行為仍是道德上許可的（morally permissible）。雙效說的吸引之處在於它的解釋力（explanatory power）。我們可以想像兩類近似的情境，一類在道德上是錯的，另一類在道德上不是錯的。要解釋兩類情境的差異，雙效說是唯一的選擇。(出處：電車難題之始源)
【第一組】
(案一)
某個城市發生凶殺案，人們鼓譟，要求法官將兇手處死，否則便要殺死五個人質。法官找不到真兇，但如果他冤枉一個無辜的人是兇手，將他殺死，便能使五個人質免於被殺。
(案二)（有兩個情境）
飛機故障，即將撞落地面。機師要決定令飛機撞去少人居住的地區，還是撞去多人居住的地區。
電車失控，前方有兩條路軌，一邊有一個人在上面工作，另一邊有五個人在上面工作。司機要決定令電車撞向一個人那邊，還是撞向五個人那邊。
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【第二組】
(案一)
六個人患重病，醫生束手無策，但如果他殺死其中一個病人，便可從屍體抽取血清，醫治餘下五個病人。
(案二)
六個人患重病，醫生手頭上有醫治的藥，但份量不足以救活六人。其中一個病人需要的份量剛好等於另外五個病人需要的總和。如果將藥給那一個病人，另外五個病人會死；相反，如果將藥給五個病人，那一個需要大劑量的病人會死。
直覺上，法官不應冤枉一個無辜的人來救五個人質，醫生也不應殺一個病人來救五個病人。在情境一棄一取五是錯的。相反，讓電車撞上一個人而不是五個人，似乎沒有錯；將藥物給五個病人而不是一個病人，似乎也無問題。在情境二棄一取五，不是錯的。第一組的情境二便是電車難題。
Foot 提出電車難題時，認為我們很明顯應該選擇讓電車撞向一人，而不是撞向五人，情況好比飛機師應該選擇讓飛機撞去較少人的地區，而不是讓它撞去多人的範圍。
(註)英國哲學家 Philippa Foot 在 1967 年發表短文 “The problem of abortion and the doctrine of the double effect” ，其中一個例子要選擇讓失控的電車撞死一個人還是撞死五個人，那個例子就是電車難題的源頭。 後來美國哲學家 Judith Jarvis Thomson 在 1976 年發表另一篇文章，標題是 “Killing, letting die, and the trolley problem” ，學界開始將同類情況稱為 “the trolley problem” ，中文翻譯是「有軌電車難題」。所以，我們的問題是：當初 Foot 用電車難題想表達甚麼？
Foot 那篇短文的討論重點是墮胎和雙效說（the doctrine of double effect）。
雙效說怎解釋兩類情境的道德差異？
在第一組案例，讓電車撞向一人，司機只是預見那一個人會死，而不是以他的死亡為目的──司機的目的是避開五人死亡的情況。相反，如果法官妥協，他的目的無可避免會包括殺死無辜的人，因為法官知道那個人不死，人們不會滿意。試想像那人在刑台上活下來的情況，法官會怎樣做？用其他方法殺死他，務求平息人們的怒意。
在第二組案例中，要取得血清無可避免要想殺人，但將藥物分配給五個病人，不需要醫生在心裡想令那個需要大劑量的病人死。簡言之，案一有壞意圖，案二只是預見壞後果，沒有以壞後果為意圖（intention）。
曾幾何時 也認為這類情境證明雙效說是對的，但Foot 她在 1967 年的文章改變立場，指出有更好的解釋方法，那個方法便是透過積極義務（positive duty）和消極義務（negative duty）來解釋兩類情境的道德差異。
「積極義務」是指做某些事的義務，例如父母有照顧子女的義務。
「消極義務」是指不做某些事的義務，例如我們有義務不偷竊、不搶劫、不殺人、不縱火。
這兩類義務本身的意思仍有待釐清，但 Foot 認為已經足夠取代雙效說，解釋情境一和情境二的差異。
根據 Foot ，關鍵在於我們一般認為消極義務比積極義務強。
法官有積極義務救五個人質，但同時有消極義務不殺害無辜，由於消極義務較強，所以他不該為救五人而害一人。
電車的情境沒有這兩類義務的衝突，唯一的分別只是死亡人數。既然無論哪個選擇都會有人死，司機應該選擇傷害最小的──撞一個人，而不是撞五個人。
同樣地，醫生有積極義務救人，但也有更強的消極義務不殺人，因此他不該為救五人而殺一人。分配藥劑的情況沒有這兩類義務的衝突，只有死亡人數不同。無論怎樣分都會有人死，醫生應該選擇傷害最小的 ─ 分給五個人，而不是分給一個人。
Foot 的理論固然可議，但回到最初的問題：電車難題究竟有甚麼作用？
根據 Foot 的說法，以前的人透過思考電車難題和其他情境的差異來證明雙效說，而 Foot 則是藉由區分積極義務和消極義務來解釋兩類情境的差異，進而反對雙效說。
無論是支持方還是反對方，在 Foot 的描述下，他們都將「電車撞一人，不撞五人」視為當然。也就是，至少對於描述整個爭論的 Foot 而言，「電車難題」根本不是一個「難題」，而是一個有明顯答案的情境：我們在電車情境應該捨一取五，不該捨五取一。【出處：電車難題之始源】
《案例》致命止痛藥 (Lethal Pain Killers)
好醫生>
(1-困境)末期病患者A忍受著異常的病痛，而要求醫生B為他注射某種會致命的止痛藥。
(2-意圖)醫生B為了減輕A的痛苦，而進行注射。(即便，可以預見注射將導致死亡)。
(3-結果)醫生B為A注射後，A死亡
(4-評估)根據雙重效果說，B依然可允許為A注射。
壞醫生>
(1-困境)末期病患者A忍受著異常的病痛，要求醫生C為他注射某種會致命的止痛藥。
(2-意圖)醫生C為了要殺死A，而進行注射。(也許，C本來就討厭A或有過節)
(3-結果)醫生C為A注射後，A死亡
(4-評估)根據雙重效果說：醫生C意圖是要把A弄死，醫生C不可允許為A注射。
上述好壞醫生面臨的道德困境、行為與結果都相同，唯一的差別只在於：其「意圖」不同。
根據「雙重效應原則」做評估的差別，則在於：
「雙重效果原則」認為，為了行善而做某事，即使預見這麼做會帶來某種惡；但只要意圖是善的，在道德上就能接受。其中的關鍵在於，預見不等於意圖，真正關鍵的是意圖。
問題是，如果A在明白止痛藥的副作用的情況下自己要求注射，而A本身已經時日無多，為A注射又確實可以幫助減輕他的痛苦，則似乎正確的判斷應該是，不論意圖如何，醫生均可為病患A注射。都是道德上可以接受。【出處：意圖與對錯-斯坎倫論雙重效果說】
這項原則會使事情往壞的地方發展，因為它可以合理化令人困窘的道德選擇。然而，若是嚴肅看待這項原則，這項原則將不只是用來自我開脫的狡辯條款。
然而，還是有吹毛求疵的人懷疑，我們對於自己行為「能預見的事」所負的責任，與我們對於自己行為「所意圖的事」所負的責任，兩者應該是相同的。如果我拿著來福槍對著森林射擊，明知此舉可能殺死過往的行人；若是真的意外殺死某人，我將沒有理由只因我沒有殺人意圖而能說自己沒有道德責任。
雙重效應原則通常都帶有四個條件。任何具有道德疑慮的行為都必須符合這四個條件，才可以得到道德上的認可而付諸實行。這四個條件是：
（1）行為者的目的必須是道德上可以接受的；他的意向必須只是正確的結果（right effect），而不能是錯誤的結果。
（2）行為本身在道德上必須是對的 — 行為本身雖會產生惡的副作用，卻可帶來善的目的；但這種行為也必須不違背道德律。
（3）善的結果必須立即實現，而且不可以依恃惡的方法 — 亦即不可以使用惡的手段來達成善的目的。
（4）惡的副作用的產生必須具有足夠相稱的理由（proportionate reason）。
雙重效果說把「後果」區分為意圖產生的後果 (intended consequences) 及可預見的後果 (foreseen consequences) 。
假設：行動者B作出會導致A死亡的行動。
根據雙重效果說， 道德上，行動者B是否允許行為，視乎A的死亡，是否因B意圖所造成的後果。
如果B的行動就是為了要殺死A（不論這是 x 的直接目的或達到其他目的的手段），則B不允許行動 。相比之下，如果B是為了其他（合理的）目的而做出行動 ，雖然同時也預見將導致A死亡，則B仍被允許可行動 。
《案例》【出處：自願被吃的豬】
「醫生，你一定要幫我。我痛苦不堪，而且我知道自己快死了。讓我解脫吧，最好是用快速無痛的方式殺了我，我已經受不了了。」
「我要確定一下，」海德博士回答：「你是要我為你注射高劑量止痛藥—也許是二十毫克嗎啡—讓你很快失去意識並且快速死亡？」
「是的！請你大發慈悲。」病人說。
「恐怕有些事是我不能做的。」海德博士回答：「不過，我瞭解你的痛苦，所以還是能做些什麼。為了解除你的痛苦，我會為你注射高劑量止痛藥，大約二十毫克嗎啡，但是這樣的高劑量會讓你很快失去意識並且很快死亡。你覺得如何？」
「這不是跟你先前的建議一樣嗎？」病人困惑地說。
「是嗎？這差別可大了！」醫生回答：「第一個建議是殺了你，第二個建議是解除你的痛苦。我不是殺人犯，而且，安樂死在我國是非法的。」
「但是不管用哪一種方式，都可以讓我解脫，不是嗎？」病人反對醫生的說法。
「是啊，」醫生說：「不過，對我來說可就有差別了。」
海德博士解釋他兩段明顯相似建議的差異，聽起來像是狡辯；他既想要實現病人的願望，又想要免於法律制裁。在許多國家，例如英國，故意縮短病人生命是違法的，即使病人處於極大的痛苦中並且要求死亡；然而，採取行動減少痛苦卻是允許的，即使可以預見此舉將加速病人死亡。判斷箇中差異的關鍵在於意圖。相同的行動——注射二十毫克嗎啡——產生相同的結果，但是意圖解除痛苦是合法的，意圖殺害則違法。 S-53 殊途同歸 (自願被吃的豬)
「電車難題」嗎？【出處：無法哲學】
「雙重效應原則」，這個原則主張，當行為會同時產生好的後果與不好的後果時，我們需要區分一件事情：如果我們將不好的後果當作「手段」，來追求好的後果，這樣的行為是道德上不被許可的；然而，如果不好的後果只是追求好後果時無法避免的「副作用」，那麼，這樣的行為可以是道德上許可的。
如果選擇將電車轉向，可以救五個人，但是無法避免的殺死一個人。此人的死亡不是為了救那五個人所採取的手段，而只是一個無法避免的副作用。因此，雙重效應原則有時被用來支持我們選擇轉向。
手段與副作用的差別，我們可以用另外一個道德哲學上著名的「炸彈例子」來理解：
《炸彈案例》
為了要盡快結束戰爭，我們有兩個選項：
(1)轟炸敵軍的兵工廠，破壞對方的軍事能力以盡快結束戰爭，然而這無可避免的會造成無辜者死亡；
(2)轟炸敵軍的難民營(難民都是無辜者、非戰鬥人員)，讓敵方國內反戰聲浪四起，以盡快結束戰爭。
根據雙重效應原則，在道德上選擇(1)是被許可的，但是(2)卻不被許可(假設在這兩個選項中，都可以使戰爭在同樣短的時間內結束，造成的非戰鬥人員死傷人數也相同)。
因為(2)是直接將無辜者的生命作為「手段」，來達到目的，意思是，如果這些人不被炸死，選項(2)就沒有意義，因此，這些人的死亡是達成目的的手段；
而(1)雖然也造成同樣多的無辜者傷亡，但是那些傷亡只是行為無可避免副作用，意思是，那麼選擇(1)的人會盡力避免這樣的後果，如果可以避免無辜者死亡，選項(1)並不依賴無辜傷亡，依然有成立；亦即選項(1)可能造成的無辜傷亡指示可預見的副作用。
【案例】Abortions when the mother's life is in danger
In cases when saving the life of a pregnant woman causes the death of her unborn child - for example, performing an abortion when continuing the pregnancy would risk killing the mother - some people argue that this is a case of the doctrine of double effect.
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This doctrine says that if doing something morally good has a morally bad side-effect it's ethically OK to do it providing the bad side-effect wasn't intended. This is true even if you foresaw that the bad effect would probably happen.【BBC】
Factors involved in the doctrine of double effect
- The good result must be achieved independently of the bad one: For the doctrine to apply, the bad result must not be the means of achieving the good one. So if the only way the drug relieves the patient's pain is by killing him, the doctrine of double effect doesn't apply.
- The action must be proportional to the cause: If I give a patient a dose of drugs so large that it is certain to kill them, and that is also far greater than the dose needed to control their pain, I can't use the Doctrine of Double Effect to say that what I did was right.
- The action must be appropriate (a): I also have to give the patient the right medicine. If I give the patient a fatal dose of pain-killing drugs, it's no use saying that my intention was to relieve their symptoms of vomiting if the drug doesn't have any effect on vomiting.
- The action must be appropriate (b): I also have to give the patient the right medicine for their symptoms. If I give the patient a fatal dose of pain-killing drugs, it's no use saying that my intention was to relieve their symptoms of pain if the patient wasn't suffering from pain but from breathlessness.
- The patient must be in a terminal condition: If I give the patient a fatal dose of pain-killing drugs and they would have recovered from their disease or injury if I hadn't given them the drugs, it's no use saying that my intention was to relieve their pain. And that applies even if there was no other way of controlling their pain.
Problems with the doctrine of double effect
Some philosophers think this argument is too clever for its own good.
- We are responsible for all the anticipated consequences of our actions: If we can foresee the two effects of our action we have to take the moral responsibility for both effects - we can't get out of trouble by deciding to intend only the effect that suits us.
- Intention is irrelevant: Some people take the view that it's sloppy morality to decide the rightness or wrongness of an act by looking at the intention of the doctor. They think that some acts are objectively right or wrong, and that the intention of the person who does them is irrelevant. But most legal systems regard the intention of a person as a vital element in deciding whether they have committed a crime, and how serious a crime, in cases of causing death.
- Death is not always bad - so double effect is irrelevant: Other philosophers say that the Doctrine of Double Effect assumes that we think that death is always bad. They say that if continued life holds nothing for the patient but the negative things of pain and suffering, then death is a good thing, and we don't need to use the doctrine of double effect.
- Double effect can produce an unexpected moral result: If you do think that a quicker death is better than a slower one then the Doctrine of Double Effect shows that a doctor who intended to kill the patient is morally superior to a doctor who merely intended to relieve pain.
【延伸議題】The Sulmasy test
Daniel P. Sulmasy has put forward a way for a doctor to check what their intention really is. The doctor should ask himself, "If the patient were not to die after my actions, would I feel that I had failed to accomplish what I had set out to do?" (假若病患經我的處置後而未死亡，是否我會認為沒有達成一開始行動的想法)
Sulmasy says it should be 'ethics as usual,' even in extraordinary times (April – May, 2020) (按我連結)
Sulmasy underscored the need to rely on "ethics as usual."
He said there should be no universal do-not-resuscitate orders for patients with COVID-19. (resuscitate: to bring someone or something back to life) The Washington Post reported that some hospitals had considered such bans because attempts to resuscitate a patient can expose health care workers to an increased risk of infection, particularly when personal protective gear is in short supply.
【延伸議題】Is it not morally appropriate to propose a universal, unilateral DNR on patients who have tested positive for COVID-19 ?
DNR，全名為Do-Not-Resuscitate(不施行心肺復甦術)。其內涵為：當病人罹患嚴重傷病，經醫師診斷認為不可治癒，而且病程進展至死亡已屬不可避免時，病人或家屬同意在臨終或無生命徵象時，不施行心肺復甦術(包括氣管內插管、體外心臟按壓、急救藥物注射、心臟電擊、心臟人工調頻、人工呼吸或其他救治行為)。
Sulmasy concurred that decisions on whether to attempt resuscitation should be made on a patient-by-patient basis, with the decision makers prioritizing patients' expressed wishes, and weighing patients' prognosis for survival. He noted that do-not-resuscitate orders may be appropriate for an individual if resuscitation is deemed to be futile care and there are two physicians certifying the decision, or the patient or a surrogate has consented, among other parameters.
When it comes to the potential for allocating scarce ventilators, Sulmasy said, it is morally acceptable to use an objective scoring system to determine a patient's prognosis with ventilator care, but there should be no unilateral policies on who gets and who doesn't get ventilator care based on age or disability. The decisions should be made on a patient-by-patient basis, in concert with ethical practice. He noted that it would be morally problematic to begin ventilator treatment and then discontinue it in order to reassign the equipment to a healthier patient, unless the patient with the ventilator, or the person holding the patient's medical proxy, refuses ongoing extraordinary care or if it becomes clear that the patient is "overwhelmingly unlikely to survive, even with treatment."
【出處】https://www.bbc.co.uk/ethics/euthanasia/overview/doubleeffect.shtml
Daniel P. Sulmasy
Daniel P. Sulmasy, OFM is Sisters of Charity Chair in Ethics at St Vincent's Hospital Manhattan, and Professor of Medicine and Director of the Bioethics Institute of New York Medical College. He is Editor‐in‐Chief of the journal Theoretical Medicine and Bioethics. His latest books are The Rebirth of the Clinic and A Balm for Gilead: Mediations on Spirituality and the Healing Arts (both Georgetown University Press, 2006).
【CATHOLIC HEALTH CARE'S RESPONSIBILITY TO COVID-19 PATIENTS AT THE END OF LIFE】(按我連結)
Statement by Sister Mary Haddad, RSM, President & Chief Executive Officer, Catholic Health Association of the United States (CHA)
"As health care providers across the globe respond the COVID-19 pandemic, there are many ethical considerations around resource allocation and the delivery of care for critically ill patients. Catholic health care is committed to the healing ministry of Jesus and upholding the inherent dignity of all who seek our care. We are also committed to accompanying and supporting patients through the end of their lives.
"Recognizing that COVID-19 is often deadly for patients with comorbid illnesses, and that even with supportive care that may include ventilators, many critically ill patients with COVID-19 will die due to conditions such as multiorgan failure, sepsis, and/or cardiomyopathy. As a result, cardiopulmonary resuscitation (CPR) may be medically inappropriate for a significant portion of critically ill patients with COVID-19 and underlying comorbidities. In keeping with the Ethical and Religious Directives for Catholic Health Care Services, if it is shown that the burdens exceed the benefits, it is morally acceptable to withhold CPR. The clinical indication for decision-making about any intervention does not change for COVID-19 patients. The best standards and any state-specific regulations or laws on end-of-life decision making are still applicable.
"It is not morally appropriate to propose a universal, unilateral DNR on patients who have tested positive for COVID-19. This eliminates clinical decision making and erodes the patient-professional relationship. Universal DNRs also fail to take into account patient and hospital-specific information and undermine our duty to treat patients as unique individuals. In all cases where a DNR is being considered, the patient and/or appropriate surrogate should be informed and provided the rationale. When such decisions are made, expert, compassionate communication with the patient and family is always necessary. Pastoral care should be consulted to provide spiritual support to all involved. Caregivers must also continue, or start, all comfort and palliative measures for the patient.
"Beyond weighing the burden and benefits of care to the patient, hospitals also need to consider the health and safety of their staff. Resuscitative measures often involve many members of the care team, use a large amount of personal protective equipment, and most importantly, have a high risk of aerosolizing bodily liquids. In light of COVID-19, it is advised that these procedures be examined and modified, if possible, to reduce staff exposure to the virus. Catholic health care's duty to care exists not only for the patient but also for the care team.
"The Catholic health care ministry has a long tradition and history of caring for patients during public health emergencies. We draw on the strength and dedication of those who came before us to provide compassionate, loving care to patients suffering from this pandemic."
This statement is based on "Code Status and COVID-19 Patient" guidelines created by the Catholic Health Association and the Supportive Care Coalition, working with colleagues at the University of Washington. The guidelines can be found here. While this decision-making model is put forth as a response to COVID-19, it is merely an application and implementation of best-practices applied to the current setting.
» Download a PDF of the Statement
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