The phrase “conscientious objection” appears to have originated from the military service and in the modern military refers to a “firm, fixed, and sincere objection to participation in a war in any form or to the bearing of arms, by reason of religious training and or belief” [3].

The oldest known conscientious objector to military service was Saint Maximilian of Tebessa who earned his sainthood for his refusal to serve in the Roman Legions on the basis of his Christian beliefs. He was executed on March 12th, 295 AD, and became a martyr for Christianity [4]. In America, the earliest known conscientious objectors were members of religious sects who refused to bear arms or take part in combat during the American Civil War. During World War I, conscientious objectors were allowed to take non-combatant military roles, but those who refused to serve in any position in the military were subjected to imprisonment and even physical abuse [1, 5]. The honorable service received by conscientious objectors, especially during the world wars, has helped to ensure the commitment of the military to the concept of conscientious objection. In fact, the first non-combat conscientious objector to be awarded the Congressional Medal of Honor was Desmond T. Doss, a Seventh Day Adventist who distinguished himself by heroic service as a medic in World War II [6]. Today, the Department of Defense criteria for conscientious objection states that “the belief upon which conscientious objection is based must be the primary controlling force in the applicant’s life” [3].

Outside of the military, conscientious objection can be witnessed in education, child immunization, and healthcare. In the United States, compulsory education varies slightly from state to state, but typically begins around the ages of 5–7 and ends between the ages of 16–18 [7]. Home schooling serves as a form of conscientious objection for many parents who would like their children’s education to have a certain religious or moral background or who object to some of the classes (e.g. sex education) or topics (e.g. evolution) offered in public schools. Similarly, school immunization laws require parents to vaccinate their children against certain contagious and fatal diseases prior to starting school. However, there are 48 states that allow for religious exemptions and 18 states that allow personal belief exemptions to these immunizations for daycare and school [8]. Many parents elect not to vaccinate their children because of a believed link to autism, although scientific evidence does not support this belief [9]. However, in 2014, an outbreak of measles occurred in the western United States leading to calls for the elimination of conscientious objection exemptions to immunization [10, 11].

The history of conscientious objection in medicine is nearly as long as its history in the military. Ironically, given the modern association of conscientious objection to abortion, the original Hippocratic Oath (written in Ionic Greek around the fifth century BC) contained the promise that “I will give no sort of medicine to any pregnant woman, with a view to destroy the child” [12]. Since the Oath was not and is not legally binding, the promise amounted to an assurance that the practitioner would exercise conscientious objection against participation in abortion. But the Oath also called upon physicians to refrain from a number of other interventions: poison, surgery (reserved for surgeons), and broadly to “refrain from injury or wrong from falsehood” [12].

In the United States, the issue of conscientious objection to abortion became acute after the Roe v. Wade decision in 1973, in which the Supreme Court found that laws banning abortion were unconstitutional [13]. Congress reacted to Roe by passing the Church Amendments that same year, which provide that “receipt of certain federal funds by any individual or entity does not authorize a public authority to require the recipient to perform or assist in the performance of an abortion or sterilization, make its facilities available for an abortion, or provide personnel to perform or assist in the performance of an abortion or sterilization” [14–16]. In 1996, the Public Health Service Act gave more specific guidelines regarding reproductive rights. These guidelines prohibit the “federal government and any state or local agencies receiving federal financial assistance from discriminating against any health care entity on the basis that: the entity refuses to undergo training in the performance of induced abortions, to require or provide such training, to perform such abortions, or to provide referrals for such training or such abortions” [15, 17]. More recently, the Affordable Care Act under Section 1303(b)(4) offers health care providers the right to conscientious objection by stating that “No qualified health plan offered through an Exchange may discriminate against any individual health care provider or health care facility because of its unwillingness to provide, pay for, provide coverage of, or refer for abortions” [18].

At the state level, 49 states provide for at least a limited right of conscientious objection for health care providers [19]. In Michigan, for example, the Conscientious Objector Policy Act allows providers to “decline care if that care compromises the provider’s beliefs, except in the event of an emergency” [20]. In Mississippi, the Uniform Health-Care Decisions Act provides that “healthcare providers may decline to comply with healthcare decisions for reasons of conscience” [21]. Vermont is the only state that offers no right of conscientious objection to health care providers [19].

Conscientious objection has philosophical support from multiple sources both in the United States and internationally. The Constitution of the United States references both a philosophical and legal basis for conscientious objection in the First Amendment [22].

The First Amendment states “Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances” [22]. The inclusion of religious freedom in the First Amendment was not an arbitrary choice by the founders. Rather, religious freedom was considered essential to American society and distinguished America (at that time) from most other countries reflecting the strong liberal (in the modern vernacular, “libertarian”) philosophical beliefs of the founders. Even in modern times, these protections retain a special place in American society and are treated with the greatest respect by American courts and governmental institutions.

Conscientious objection in the United States is supported primarily by the First Amendment. Certainly, it is argued, one cannot be forced to perform acts contrary to one’s religious or ethical beliefs any more than one can be forced to, for example, pray to a god one does not believe in. Indeed, with respect to religious freedom, the Supreme Court has been particularly sensitive, applying a “strict scrutiny” test to any failure by the government to accommodate religious beliefs and requiring states to show a “compelling interest” for such failures of accommodation [23].

Outside of the United States, a right of conscientious objection is supported by a number of other countries and international organizations. Article 9 of the European Convention on Human Rights provides an explicit right to freedom of thought, conscience, and religion [24]. Though not absolute, Article 9 does provide support for European physicians to conscientiously object to participation in certain care [24]. The British Medical Association supports a conditional right to conscientious objection, and by statute, British physicians may conscientiously object to participate in abortion and fertility treatments [25].