My dog Mu is very, very good. Obviously. Except of course, when she is a bit bad—or mischievous, say—like last week when she ate a whole chocolate mousse cake I ever-so-briefly left unattended on the counter.

Afterward, she eyed me sheepishly with a milk chocolate stain on her sweet face, and I felt certain Mu knew she did something she wasn’t supposed to do. Also, it appeared that she did it deliberately because she waited for me to disappear, which implies that she restrained herself in my presence and could have done the right thing theoretically.

To call her behavior bad, however, assigns it a morality that some philosophers would say Mu doesn’t possess. She can only be bad if she can distinguish this behavior from goodness, which many argue is a capacity that is distinctly human.

Does a dog know right from wrong? It’s a question philosophers have long pondered, coming to a slew of different conclusions.

Mu—whose full name is Tao Pi Mu—got her moniker from a Zen koan known as “the Mu koan.” It’s a philosophical riddle which has been around since the 9th century and asks, “Does a dog have Buddha nature?” According to Buddhist lore, a student asked this of Zen master Zhao Zhou and he replied, “Mu!” This reply (無) is alternately interpreted as Chinese for “no,” or “nothingness,” or the sound of a dog barking, in which case it might mean “yes.”

Today, Zen masters ask the question of students to prompt thinking beyond words. But T. Griffith Foulk, professor of Asian religions at Sarah Lawrence College—who also has a dog named Mu, short for Mustafa—explained in Tricycle in 1999 that Zhao Zhou wasn’t being coy. There was at the time a lively discussion among Chinese philosophers about the inner lives of animals.

After he exclaimed, “Mu!” Zhao Zhu added that all sentient beings do in fact have Buddha-nature, dogs included, meaning that they can be compassionate, or good. Foulk writes that the Zen master “may simply have wished to stress the point that although living beings have Buddha-nature, unless they realize that fact by seeing the nature they remain caught up in delusion and continue to suffer.”

Awareness is also emphasized in discussions of animal morality in the western philosophical tradition. In 1798, Immanuel Kant wrote that “the fact that the human being can have the representation ‘I’ raises him infinitely above all the other beings on earth. By this he is a person….that is, a being altogether different in rank and dignity from things, such as irrational animals, with which one may deal and dispose at one’s discretion.”

In other words, Kant didn’t believe a dog like Mu could think or distinguish between bad and good because she isn’t self-aware. For this reason, she is not moral. This view—which is known as human exceptionalism—persists today.

But increasingly philosophers and scientists argue that animals are moral and that we humans may just be insufficiently aware of their inner lives to understand how or why they decide to do what they do. For example, Mark Rowlands, a professor of philosophy at the University of Miami, and author of The Philosopher and the Wolf, among other books, believes his dog and wolf are good.

Rowlands raised a baby in the company of this wolf and dog. He says the creatures were gentle, caring, and showed a “Zen-like” tolerance of the young child’s wild antics. He defines goodness as a kind of concern and points also to animal studies and anecdotes that show animals caring for other creatures—including people—taking risks to save them, and hurting them too, as proof that they can be both bad and good.

However, because animals may not necessarily be able to scrutinize their behavior—or reflect on the reason they act—he argues in the Philosopher’s Magazine, they cannot be held responsible for their actions even if they are bad. From Rowland’s perspective, they are moral creatures even if they are not rational; in this sense, he is like Zhao Zhou, recognizing their Buddha nature but doubtful of their self-awareness.

Rowlands is distinct from Kant, however; he doesn’t elevate humanity just because we are self-aware. And he points out that we’re not entirely rational either. Humans too do plenty of things thoughtlessly, impulsively or instinctively—we don’t always scrutinize our actions in advance or know why we’re doing good or bad. If a person were to run into a street to save a child from the danger of an oncoming car, it wouldn’t require thought as much as instinct.

Perhaps then, humans and animals are both hardwired for morality. Some scientists, like Marc Bekoff, an ecologist at University of Colorado, Boulder, believes that morality is a common evolutionary trait of all mammals. He argues that an innate sense of justice—right and wrong, good and bad—serves as the “social glue” that maintains group harmony in aggressive and competitive groups.

He notes that it may be difficult for humans to recognize morality in a pack of wolves or baboons, however, because we don’t know the precise needs and rules of other species’ societies. What is clear, however, is that many species live together and follow codas. They have law and order, a set of acceptable and unacceptable behaviors that are somehow communicated and followed.

Not only that, animals can extend their sense of justice or empathy to other species, not just their own kind. Bekoff wrote a book called Wild Justice with moral philosopher Jessica Pierce, also from the University of Colorado. She told the Telegraph in 2009, “There are cases of dolphins helping humans to escape from sharks and elephants that have helped antelope escape from enclosures. While it is difficult to know for certain that there is cross species empathy, it is hard to argue against it.”

Frans De Waal, an Emory University primatologist, also thinks ethics are inherent in animals. Morality “is not as much of a human invention as we like to think,” he proposes in his 2016 book Primates and Philosophers: How Morality Evolved. De Waal argues that humans err when they understand morality as the unique veneer that keeps us in check and separate from animals.

People do resist the idea of animal morality though—and that is in part because it calls our own goodness into question. As the Stanford Dictionary of Philosophy points out, recognizing the capacity for compassion, virtue, suffering, and struggle in animals puts humans in an awkward position. If we recognize them as moral beings with ethical claims, we’ll have to behave better ourselves.

Perhaps it’s not Mu who is bad when she steals my chocolate mousse cake, but me—the human who walks her on a leash—whose morality should be questioned.