Good people can do bad things and sometimes do. Why? A useful analogy explains some of the reasons.

A person visits a doctor where she is told that she has acid reflux. That’s a description. Next, the doctor tells the patient what to do for the condition. That’s a prescription.

Perhaps the diagnosis is wrong. It wasn’t acid reflux at all but gallstones. The patient winds up being treated for the wrong illness. So if someone’s understanding of a moral situation is faulty, they may think they are acting ethically when in fact they are not. This is where learning how to analyze a situation correctly from an ethical point of view is important.

Back to the medical analogy: Things may go wrong even when the physician’s diagnosis and prescription are right because the patient doesn’t follow through. This is where matters move from the philosophical to the psychological.

According to the Center for Spirituality and Healing at the University of Minnesota, “Fear can interrupt processes in our brains that allow us to regulate emotions, read non-verbal cues and other information presented to us, reflect before acting, and act ethically.”

Fear impedes ethical decision making in another way. Fear of physical harm is obvious; less obvious is the fear of being different. Our lives are bound by social and cultural norms and expectations. While some norms are morally positive (don’t lie), others neutral (don’t use your hands when eating), some can be harmful (some groups are inferior). To go against group norms is difficult as it may lead to ridicule and exclusion. Knowing what is right and acting upon it can be set aside in order to belong.

The power of conformity makes it hard to act morally when others around you disapprove. As explained by the McCombs School of Business, University of Texas, “The conformity bias is the tendency people have to behave like those around them rather than using their own personal judgment.”

Perhaps the most insidious impediment to ethical behavior is implicit bias, “a form of bias that occurs automatically and unintentionally, that nevertheless affects judgments, decisions, and behaviors.”

Stanford psychology professor Jennifer Eberhardt explores how implicit biases shape our perceptions and behavior particularly in regard to race. In her book, Biased, she shows through numerous studies how hidden prejudice “affects all sorts of decisions we make during the normal course of our lives—the homes we buy, the people we hire, the way we treat our neighbors.”

Eberhardt points out that hidden prejudices, ones that we don’t know we hold, apply as well to biases related to “age, weight, ethnic origin, accent, disability, height and gender.”

These three reasons why people with good intentions don’t act ethically—having wrong information, being afraid to go against the crowd and having hidden biases—are perhaps the most important. Recognizing these fault lines opens the way to education (how to make good ethical decisions) and empathy (putting yourself in place of another), the groundwork of a moral life.