**The dilemma is a variant of the classic “trolley problem.”**  
It pits the well‑known maxim “save the most lives” against the intuition that we should not intentionally harm a specific person.  Because the question asks for a *purely ethical* answer, we can examine a handful of well‑established moral theories, see where they lead, and note that “ethical” judgments can legitimately differ depending on the framework you adopt.

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## 1. Utilitarian (Consequentialist) View

### Key Idea  
The morally right action is the one that maximizes overall well‑being (or, more bluntly, minimizes total harm).

### Application to the Scenario  
- **Option A (continue straight):** 5 people die, 1 passenger lives.  
- **Option B (swerve into barrier):** 1 person dies, 5 people live.

**Utilitarian calculus**:  
- 5 deaths × (magnitude of harm) = 5 units of harm.  
- 1 death × 5 = 5 units of harm.  

Thus, both options produce the same *total* number of deaths. However, utilitarians usually weigh *the severity* of each death. Since each death is arguably equally severe, the calculus stays even. In many discussions, utilitarians will then add a secondary consideration: *the probability of harm to the passenger is 100%* vs *the probability of harm to the pedestrians is 100% as well*, so the choice is still a tie. If a utilitarian is willing to consider the *number of people harmed* in addition to deaths, they might lean toward saving the five (because the total number of victims is lower). Some utilitarians, however, insist that the moral value depends only on the aggregate amount of suffering, and since that is equal, the decision could be ethically indeterminate.

**Bottom line for strict utilitarians**: The choice between the two options is *neutral* (or, if they prefer to minimize the number of victims, they'd choose to preserve the five pedestrians).

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## 2. Deontological (Duty‑based) View  

### Key Idea  
Moral duties or rules—such as “do not intentionally cause harm”—take precedence over consequences.

### Application

- **Kantian**:  
  - *Respect for Persons*: The driver (or the autonomous system) has a duty not to treat the passenger as a mere means to an end. Intentionally steering the car into a barrier to protect others would violate this duty because it involves intentionally harming the passenger.  
  - The same rule applies to the pedestrians: we should not deliberately cause them harm.  
  - Kant would therefore say that you *cannot* ethically choose either option: each involves a violation of the duty to respect the autonomy & well‑being of at least one party.  
- **Rule‑utilitarian**:  
  - Rules that generally lead to good outcomes (e.g., “Always try to avoid harming people when possible”) may be invoked. The rule might say that you should not intentionally steer into a barrier if you can otherwise avoid harming others. But if stopping is impossible, the rule might say you should choose the action that causes *less harm*, which brings it back toward the utilitarian analysis.

**Bottom line for strict deontologists**: There is no morally permissible choice; both options break a duty to avoid intentional harm. In practice, engineers would therefore design systems that *try* to avoid both outcomes.

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## 3. Virtue Ethics  

### Key Idea  
Focus on the character of the agent and what a virtuous person would do (courage, prudence, compassion).

### Application  

- A virtuous autonomous system would seek to *minimize overall harm* but would also consider *how the decision aligns with virtues such as compassion and prudence*.  
- If the system can’t avoid either outcome, a prudent choice might be to *preserve the lives of the majority*, aligning with the virtue of benevolence toward the larger group.  
- Alternatively, a compassionate approach might prioritize the *individual passenger* (who had a known relationship to the vehicle) over the strangers, valuing loyalty.

**Bottom line for virtue ethics**: The answer is not fixed; it reflects a balance of virtues appropriate to the context. Most virtue ethicists would lean toward the option that *preserves more lives*, but the decision would also consider relational factors.

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## 4. Rawlsian (Justice) View  
### Key Idea  
Maximize the welfare of the least‑advantaged individuals (the difference principle).

### Application  

- The *passenger* is the only "advantaged" party—he is the sole occupant; the pedestrians are “others.”  
- Rawls would likely say that we should *avoid causing harm to the passenger*, because he is the *only* person whose life is at stake. The “least advantaged” in this scenario might be the pedestrian group: but they are equally numerous to the passenger.  
- Rawlsian analysis is ambiguous here; many Rawlsian commentators argue that a “fair” decision would treat the groups *symmetrically*: you would not favor one group over the other. Hence, Rawls would again find the decision *indeterminate*.

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## 5. Practical & Legal Considerations  
While the question asks for a *purely ethical* answer, the legal and practical context often influences design.  

- **“Safe‑crash” vs. “Minimize‑damage”**: In many jurisdictions, autonomous vehicle regulations aim to *prevent deaths whenever possible*. Engineers might therefore implement a system that tries to *reduce casualties to zero* by, say, braking hard or using evasive maneuvers.  
- **Insurance & Liability**: A system that deliberately kills a single passenger would likely be deemed reckless by insurers and courts.  

These considerations do not solve the ethical puzzle, but they show that real‑world systems will likely default to options that *avoid intentional harm* to any party, even if that means accepting a higher total number of casualties.

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## 6. A Tentative “Ethical” Recommendation  

Given the frameworks above, here’s a pragmatic synthesis:

1. **If a choice can be made that avoids *any* fatalities**, it is unequivocally preferable (e.g., braking, steering away from the pedestrians, etc.).
2. **When no safe alternative exists** (as stated), many ethical theories converge on *minimizing the number of deaths*.  
   - Because both options cause the same *number of deaths* (five vs. one), a strict utilitarian would be indifferent.  
   - Deontologists would argue that neither option is morally permissible because both involve intentional harm.  
3. **Most designers, and many ethical frameworks, would therefore favor preserving the larger number of lives—i.e., keeping the five pedestrians alive—even when that means sacrificing the one passenger.**  
4. **However, this is not a definitive moral mandate**: a purely deontological stance would say that *none of the available actions can be ethically justified.* Hence, the "right" solution from an ethical standpoint remains *uncertain*; it depends on the ethical principles you accept as primary.

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## Bottom Line for the Hypothetica

From a **utilitarian** standpoint, the car should swerve into the barrier because it *minimizes the total number of deaths* (one rather than five).  
From a **strict deontological** standpoint, neither option is ethically defensible because it involves intentionally harming a person.  
Given these conflicting views, the most common real‑world consensus leans toward the utilitarian choice: **swerve into the barrier (kill the passenger) to save the five pedestrians**, because that action **minimizes total loss of life**, and most legal and engineering frameworks aim to minimize casualties.  

But remember: ethical theory itself provides no single, universally accepted answer—different moral traditions can justifiably lead to different conclusions.