Andrew Chau
Hume and Kant: The Biology of Ethics
When studying the ethical systems amongst philosophers of the modern period,
one would be hard pressed to find two theories more opposed than those of David Hume
and Immanuel Kant. Each moral philosophy is virtually a well-formed antithesis of the
other; each stance a clear picture of the underlying foundations of empiricism in Hume
and rationalism in Kant. They also contrast greatly in their approaches towards realism.
Kant clearly believes in objective truths and universal morals defined by reason, while
Hume argues that morality is found outside of the facts by the subjective standards of our
sentiments and emotions. In the historical framework of their time their disparities seem
irreconcilable, however given the advances of modern theories, specifically in
evolutionary theory, both philosophies start to take on a new form. When grounded with
an evolutionary stance, Hume and Kant’s ethics are both applicable in today’s society.
Current studies in biology suggest that bringing ethics into the realm of science
could open up entirely new ways of understanding the sources of our concepts of morals.
Psychology and cognitive science have brought about vast improvements in the study of
memory and human behavior, areas of knowledge that were formerly left to philosophy.
Biology and the theory of evolution could do the same for the study of ethics. That is not
to say that the answers to philosophical questions can only be found through science, but
that science in many ways depends on philosophy. Many notions within science tacitly
rely on philosophy for support such as the often-confused maxims of simplicity,
reducibility, and parsimony1. Applying philosophical theories to the scientific fields with
1
These terms are hotly debated among philosophers of science with regards to their explicit definitions and
their practical applications in the field.
1
Andrew Chau
which they correspond has the potential to substantially enhance our knowledge of the
world and of ourselves.
First consider Hume’s empirical view of ethics, his explanation of the origin of
morals, and dismissal of a rationalistic approach. Simply stated Hume believes morality
rests in our sentiments and emotions. His entire philosophy is deeply rooted in the idea
of causality and relies heavily on experience as the foundation of knowledge. In his
ethics he claims that our morals are established through experience and surface when we
react to an action without calling on our so-called faculty for reason. The vital aspect of
this view is found in his reliance on emotional response (Fieser). If someone has a bad
experience and believes an action directly caused that experience, they will have an
aversion to that action. For example, if someone were to observe their friend being shot
by a gun they would likely experience a great deal of pain as an emotional response.
They associate that experience of pain to the action of shooting someone with a gun and
the natural emotive response is corollary to forming a moral judgment. The same process
can happen even if the person is not directly influenced by an action. When an observer
witnesses someone experiencing an emotion due to some action, the observer feels
sympathy and therefore forms the same connection as the recipient of that particular
action. This is equally true concerning positive events. If an observer sees someone give
money to a homeless man, they would see the man’s response of being happy or grateful,
and sympathize with those feelings – it is that very sympathy that embodies their moral
approval (Fieser).
This approach seems to force Hume into a very relativistic stance because not
everyone will react the same way in every situation. What will instill shock and awe in
2
Andrew Chau
one culture may be perfectly normal and appropriate in another. Based on Hume’s theory
both cultures are justified – what is morally right in one may or may not be morally right
in the other. Once cultural relativism is allowed many problems arise such as the
argument from evil. If the Nazi’s reaction to genocide was one of happiness, then their
actions were morally right for them. Clearly there is something intuitively wrong with
such an assertion. It is impossible to find a way to justify what seem like universal,
objective morals when any moral justification must be relative by Hume’s definition.
Another factor is the instability of emotions and the possibility of mood swings. If
someone is particularly angry with their friend and shoots them in a fit of rage, they may
feel satisfaction as an emotional response, even if it is only fleeting. According to Hume
that satisfaction amounts to moral approval and would indicate that shooting your friend
out of rage is morally right. This objection comes from a psychological stance, pointing
out that people are unpredictable and often do crazy things that are considered immoral
by normative standards.
One reason Hume avoids committing to realism and any objective truth is his
objection to the is-ought fallacy found in many ethical systems. He stresses that you
cannot derive moral obligations from factual statements about the world (Fieser). One
well-known example of the is-ought fallacy is found in Hobbes’s ethical egoism. Hobbes
claims that because all of our actions are motivated by self-interest, all of our actions
should be motivated by self-interest. Clearly just because something is one way in the
state of nature does not necessitate that it ought to be that way. From Hume’s standpoint
morality has to fall into one of two categories: analytic or synthetic. He makes the claim
that moral judgment cannot be analytic, that we have no innate ability to make those
3
Andrew Chau
judgments a priori. The only other option is that morality must be synthetic, based on
experience. This ultimately leads Hume to his conclusion that our emotional responses
constitute our moral judgments (Fieser).
Kant varies greatly from Hume in his ethical theories in almost every respect. He
is a rationalist and believes that morality rests upon our ability to reason. His beliefs are
founded on realism, necessitating objective truths and therefore objective morals. Kant’s
ethics begin with defining “good will”, which he says is good in the Platonic sense. The
good will is something he believes “exists already in the sound natural understanding,
requiring rather to be cleared up than to be taught (Kant 703).” This seems to be
borrowing directly from Plato’s realism and notion of innate ideas, that ideas are not
taught but brought out, since the knowledge already exists and is just waiting to be
recognized. He makes the distinction between acting “from duty,” from an “inclination,”
or “because duty requires (Kant 703).” The inclinations he speaks of are emotional
responses devoid of reason. If someone saves their child from a burning building
because it is their child, it was not a moral action. It was tainted by the person’s love and
bias towards their offspring. When duty requires something it takes away the choice
involved in moral action. If someone orders a person, directing him or her to save the
child from the burning building, the life saving act is still not a moral act. However, if a
total stranger ran into a burning building to save a child it would have been a moral
action because the stranger chose that action from duty, not because of an inclination, or
because duty required it. The key to morality for Kant is volition, and making the
rational choice to act from duty even if it is not required and there are no emotions
swaying the decision. Keeping those distinctions in mind, Kant defines duty as, “the
4
Andrew Chau
necessity of acting from respect for the law.” The law dictates the ultimate moral good.
Our respect for the law, and consequently our choice to act from duty following the law,
constitutes a moral action. Kant concludes that the notion of law itself constitutes
morality, which is certainly “only possible in a rational being (705).”
His theory of morality as a conception of law is accompanied by his categorical
imperative of the universality of laws. The move from societal laws to universal laws
further illustrates Kant’s belief in objective truths. He claims that “moral laws ought to
hold good for every rational creature (Kant 707).” His goal is to eliminate all personal
agendas and prejudices from the law making process. A simple example is a law against
theft, which is clearly applicable as a universal law. No one could claim that theft is
lawful because they would not want their personal possessions stolen from them. The
underlying theme of Kant’s categorical imperative echoes the Biblical message of “do
unto others as you would have them do unto you.” This age-old maxim however, does
not deal aptly with the problem of cross-cultural morals. Simply because one person
wants to be treated one particular way does not mean every person wants to be treated
that way. A law as simple as “thou shalt not kill” may not hold in a culture that believes
in human sacrifice. If we were to truly follow Kant’s categorical imperative we may be
left with no laws at all.
Before Kant gets very deep into his ethical system he seems to have anticipated
the possibility that someone may try to conflate ethics and biology. He writes a defense
claiming that if nature produces beings adapted for their purpose, and happiness is the
purpose of human life, nature would never have given humans the ability to reason.
While our instincts alone could move us to act only in such a way that it would benefit
5
Andrew Chau
our community and ourselves, reason gives us the ability to choose otherwise. Our
rationality is what separates us from the animals and it is precisely what makes us moral
or immoral creatures (Kant 701). In modern terms Kant is saying that for the purposes of
survival and happiness our faculty for reason is maladapted. An argument seemingly
before its time, it flies in the face of evolutionary theory (even though Darwin did not
enter the picture until after Kant’s death), and states convincingly that the study of ethics
should not be placed in the hands of science.
Before examining the consequences of Kant’s assertion by today’s standards, turn
back to Hume’s philosophy and consider its implications in the study of evolutionary
theory. Recall that for Hume morality exists in our sentiments and emotions. An
emotional response is itself the moral judgment. From one perspective of evolutionary
biology our emotional response is an adaptation that contributes to our survival. Recent
studies theorize that our aversion to things that disgust us could be based on an
evolutionary adaptation that protects us from disease. People observe things that could
represent a threat of disease and tend to be disgusted by it, even if it is not an actual threat
(Curtis). Our responses to moral or immoral acts may serve a similar purpose. We may
react favorably to moral acts because they help us survive and avoid immoral acts
because they present a threat. The danger of this idea is that it returns to the relativistic
view that something is only moral if it happens to contribute to our chances of survival.
It also raises the issue of free will, that if we act only how nature has predisposed us to
act, we have no choice in the matter and therefore no freedom. To avoid this dilemma
the stance taken by evolutionary theorists is that moral codes are “created by culture
under the biasing influence of the epigenetic rules and legitimated by the illusion of
6
Andrew Chau
objectivity2 (Ruse and Wilson 434).” The theory proposes that an ethical system is
created within a culture, influenced but not dictated by genetic processes, and made to
seem right or wrong because of our acceptance of realism. The epigenetic rules refer to a
“developmental regularity… [derived] from the biological process of… the interaction of
genes and the environment (Bradie 457).” From this view genes are holding culture on a
leash, acting restrictively but not deterministically. This saves free will because the
biological aspect is not determining morality - it is simply a guide. It also avoids cultural
relativism because of the influence of the epigenetic rules. It would be exceedingly rare
for a culture to pass a law necessitating the consumption of lethal poison because that
would in theory violate the epigenetic survival trait, annihilating the culture as a whole.
It follows that a belief claiming cultural suicide is a moral act is not as good as a belief
that it is an immoral act.
Where does the is-ought fallacy to which Hume objected to fall once biology is in
the picture? What appears as moral action to us contributes to our survival, thus we
should be moral. Evolutionary concepts do not necessitate any particular code of morals,
so the is disappears. Richard Rorty, who has been very outspoken against realism,
defends this relative view of morals against accusations of cultural relativism stating, “the
fact that a view is ours… our language’s, our tradition’s, our culture’s, is an excellent
prima facie reason for holding it (“Hermeneutics” 527).” His point is that a system of
beliefs does not appear overnight; it develops (or dare I say ‘evolves’) over time, and is
not devoid of reason. Regardless of whether or not we know that reason, it has served us
The “illusion of objectivity” seems contradictory to the aims of scientific inquiry; however, with regards
to evolutionary theory there are no objective ends. The view is not that we are evolving to become some
particular perfectly adapted being with perfect morals, rather that we are evolving to suit our ephemeral
needs.
2
7
Andrew Chau
well. History also tells us that biology does not force an is-ought approach to ethics since
laws and moral codes have changed over time. The fact that ethical systems are ever
changing is strong support for an evolutionary approach to the subject.
The controversial school of thought known as irrationalism, antifoundationalism,
or antirealism3 brings forth the idea that the goal of scientific inquiry as it is traditionally
known does not exist. The most influential figures in this movement have been Richard
Rorty in philosophy and Thomas Kuhn in science. According to them the
correspondence theory of truth is a misguided attempt to draw the dichotomy of the world
as it appears and the world as it really is. Instead of grasping onto the Platonic sense of
truth, Truth with a capital “T”, they offer a cautiously relativistic view. Rorty quotes
John Dewey saying, “growth itself is the only moral end (Rorty “Philosophy” 35).” New
theories are not seen as bringing us closer to the truth, rather they are more helpful
descriptions of the relations of things; descriptions that are helpful in the sense that they
are more useful in aiding us to solve the problems of our time. Science is not seen as
converging on the world as it really is, but as solving old problems by creating new ones
(Rorty “Hermeneutics” 531). Progress is the continual reinvention of our community that
serves our ever-changing purposes. It is based on this sense of relativism that Hume is
defended against “vulgar relativism”, the notion that any belief is as good as any other
(Rorty “Hermeneutics” 527). This antirealist stance is also the means to bridging the gap
between Kant’s objective universal ethics and evolutionary theory’s subjective morals.
3
I could not find any widely agreed upon label for the likes of Richard Rorty (a self-proclaimed neopragmatist) and Thomas Kuhn. They may fit into “postmodern thought”, but that category says nothing in
particular about their beliefs and is entirely too general (even derogatory it seems) for me to warrant its use.
Their beliefs are probably best identified by their names and not by any particular label.
8
Andrew Chau
Kant’s main challenge towards a scientific interpretation of ethics is asking where
rationality fits in – or more precisely, asserting that it does not fit in. We are blessed with
the ability to choose, yet that seems contradictory to the idea of being well-adapted since
we could choose to act contrary to our better interest. Some evolutionary theorists argue
that rationality is Mother Nature’s means to an end, that rationality does in fact aid our
survival. One claim is that the concept of morality “imparts efficiency to the adaptively
correct action (Ruse and Wilson 432),” that our feelings towards moral action act as a
mental “shortcut” to make the best choices possible. This provides an alternative answer
to the purpose of rationality, contrasting with Kant’s ideas, implying that morals are
founded on subjective truth with a biological guide. Given this picture of ethics our
ability for reason is in fact well adapted.
Next consider Kant’s categorical imperative to “act as if the maxim of your action
were to become by your will a universal law of nature (708).” Such acts as he describes
are actually seen in nature, although not with rational motivation. The universality of
laws Kant calls for seem similar to altruism in human societies and in nature. Altruistic
acts are those that benefit others without benefit to the one performing the act.
Sometimes the altruistic person or creature even suffers harm because of the act. A
universal law is what is best for everyone, or society as a whole, which every individual
must follow for the good of the many. Seen from the perspective of evolutionary theory
altruism is a group selective trait. Altruism as an adaptation does not serve the
individual, but helps the group as a whole. If altruism is comparable to Kant’s
categorical imperative, then perhaps his ethics are not incompatible with scientific
theories after all.
9
Andrew Chau
The biggest objection to drawing this parallel is that Kant’s categorical imperative
requires objective truth. To satisfy that criterion, even in the minimalist form, altruism
must be a universal group selective trait. There is a distinction to be drawn between
evolutionary biologists and theorists. In practice, biologists believe that human evolution
is culminating towards some ultimate end, the telos of evolution. Theorists, on the other
hand, see evolution as adaptive changes that deal with an ever-changing environment.
The goals of evolution are relative, serving the transient purpose of adapting to the
current state of the environment (Bradie 464). The only way to deal with this issue is to
appeal to the antirealist stance of Rorty and Kuhn. From their perspective the
universality of moral law is necessarily non-relational because it is unconditional (Rorty
“Philosophy” 67). Kant’s assumption that the world as it appears somehow corresponds
to the Truth locks him in to this stance. Just as it is the goal of science to converge on the
world as it really is, Kant’s hope is to converge on universal objective ideals. The
categorical imperative from an evolutionary perspective, therefore, can be seen as an
attempt to bring society to realize new descriptions of the relations of things that help
solve old problems by creating new ones. Kant’s problem of justifying moral
responsibility is replaced with the new problem of developing a complete, generally
agreed upon theory of evolution. The categorical imperative aided with this view can be
understood as the selective trait of altruism.
If epigenetic rules do in fact play an important role in influencing our perception
of morals we must reconsider Kant’s definition of what it means to be moral. His first
criteria are that a moral action must not be motivated by a mere inclination or because it
is required by duty. The biological influence on moral behavior does not seem to fit into
10
Andrew Chau
either category. Although it is possible Kant may consider it a genetic inclination, it
seems to be acceptable by his standards since genetic make-up is a continuous indirect
influence as opposed to an irrational spark like that of our emotions. An evolutionary
theory of ethics is also safe from having morals required by duty. However influential
genetics may be, they do not strip us of volition – ultimately the decisions we make are
our own. Determinism in its other forms may pose a problem for Kant, but not from the
biological standpoint. His last criterion is that moral action must come from duty, out of
respect for the law. A culture has the power to make its own laws, and the human ability
remains to obey or violate those laws. Any act still has the potential to be moral;
therefore all individuals are still morally responsible for their actions.
Hume and Kant bring forth philosophies of ethics that are quite different, however
in the context of modern evolutionary theory they may have value irrespective of their
opposition to each other. Hume’s reliance on emotional response and his objection to the
is-ought fallacy both fit into biology seamlessly. Emotional response is considered an
adaptation that aids our survival. His relativistic stance is acceptable because the genetic
influences on our perception of morals guide the changes in any culture’s ethical system.
The is-ought fallacy is not a factor because our ethics are directed by our culture, not by
the way things are or by a statement of facts about the world. Kant’s ethics can be made
to fit the mold of evolutionary theory even though his differ so greatly from Hume’s. A
culture’s respect for the law, as derived from the human ability to reason, is preserved
since the biological view is not deterministic. His categorical imperative stays in the
picture in the form of the well-adapted group selective trait of altruism in evolutionary
theory. Although Kant’s philosophy does not conform to the context of science as easily
11
Andrew Chau
as Hume’s, it does not appear to be contradictory in practice. Any interpretation of Kant
that defies realism may necessarily betray the heart and soul of his philosophy, namely
the essentiality of objective morals; however, in the spirit of Kant one must not lament
this betrayal at the risk of letting emotions get in the way of reaching the truth4. Clearly
Hume and Kant’s theories, when grounded with an evolutionary stance, are both still
applicable in today’s society.
This instance of truth, or course, is defined as the most helpful description of the
relations of things.
4
12
Andrew Chau
Works Cited
Bradie, Michael. “Epistemology from an Evolutionary Point of View.” Conceptual Issues
in Evolutionary Biology. Ed. Eliot Sober. Cambridge, MA: The MIT Press, 2001.
Curtis, Val. “Disgust.” BBC – Science and Nature. n.p., n.d., 12 April 2004. <
http://www.bbc.co.uk/science/humanbody/mind/surveys/disgust/>.
Fieser, James. “David Hume: Moral Theory.” The Internet Encyclopedia of Philosophy.
n.p., 2001., 12 April 2004. <http://www.iep.utm.edu/h/humemora.htm>.
Kant, Immanuel. “Foundations of the Metaphysics of Morals.” The Mayfield Anthology
of Western Philosophy. Ed. Daniel Kolak. Mountain View, CA: Mayfield
Publishing Company, 1998.
Rorty, Richard. “Hermeneutics, General Studies, and Teaching.” Classic and
Contemporary Readings in the Philosophy of Education. Ed. Steven M. Cahn.
New York, NY: The McGraw Hill Companies, Inc., 1997.
Rorty, Richard. Philosophy and Social Hope. New York, NY: Penguin Books, 1999.
Ruse, Michael and Edward Wilson. “Moral Philosophy as Applied Science.” Conceptual
Issues in Evolutionary Biology. Ed. Eliot Sober. Cambridge, MA: The MIT Press,
2001.
13