Meeting 4.3 – Biological and Theological Altruism

On 2 March, the reading group met to discuss ideas of altruism in biology and theology.


The word “altruism” has come to be used in a variety of ways, so we started with a dictionary definition.

Altruism: “1. The belief in or practice of disinterested and selfless concern for the well-being of others. 1.1 Zoology Behavior of an animal that benefits another at its own expense.” OED Online

Normally, I defer to the Oxford English Dictionary, but in this case, I fear that both definitions can be misleading.  It highlighted for me four different issues, worthy of consideration.

Self-interest versus Selflessness: Do you consider your own well being when you decide on an action? Do you think of your individual interests? Do you consider broader self interest, that is the collective interests of your group as opposed to other groups? Self-interest need not exclude universal interests of the interests of others. It’s only a question of whether you consider yourself.

Other-interest versus Apathy: Do you consider the well being of others when you decide on an action? Do you think of the interests of all others, or some subset of others?

Relative interest: Do you weigh interests against each other?

Intention: To what extent do these processes take place rationally, objectively, consciously, or willfully? It’s possible to choose subconsciously or to fall into habits of behavior without thought.

Historically, the word was advanced by Auguste Comte in 1830 as an antonym to egoism.


Altruism has been seen as mal-adaptive, by definition, making it a challenge for biologists after the Modern Synthesis. [Mal-adaptive: leading to shorter survival time and/or fewer offsping, selected against.]

Wynne-Edwards (1962) proposed inter-deme selection (between population) as an explanation, but later research suggests this force would be swamped by intra-deme forces. Selfish individuals within a population would take over in that population even though as a whole it was out-competing other populations. In the long run this seems insufficient to produce regular altruism. [David Sloan Wilson is one of the chief advocates for “group selection,” believing that there are situations in which inter-deme selection can lead to altruism.”

Hamilton (1963) formalized kin selection (favoring relatives). “Would I jump in a lake / to save my drowning cousin? / It’s not a risk I’d take / for him plus half a dozen. / But if you raise the stake / and make the prize my brother? / Now that’s a deal I’ll make… / if you’ll just toss in another.” Inclusive fitness makes the success of relatives into individual adaptation. By including the benefits to kin, you reveal how natural selection can promote traits that harm self but help others – provided the others are related.

Trivers (1971) suggested reciprocal altruism (leading to future relational benefit). By counting the advantages of future reciprocation from those helped, you reveal how natural selection can promote traits that harm self but help others – provided the others have an opportunity and a tendency to pay you back. Note that it need only be a probabilistic tendency to reciprocate; it need not be a guarantee. Nor is necessary for the future benefit to go to you; reciprocation may help your kin. [Game theory suggests that, with multiple games, optimal strategies avoid prisoner’s dilemma and tragedy of the commons type problems through short-term altruism.]

Note that all three theories explain spite (selfless punishment of others) as well as altruism (selflessly helping others).

Biological Altruism has come to mean explanations of behavior that are not, in fact, altruistic. Biological altruism applies to traits that are in your collective, family, or long-term self-interest even though they are not in your immediate self interest.


Bearing this in mind, I have updated an earlier breakdown of types of altruism. It began as a summary of discussion with Anna Dornhaus and the Forum on Chance, Purpose, and Progress at the University of Arizona ( For the sake of clarity, I provide equations with the following variables:

Personal Benefit (P) – what the individual gets out of an action

Inclusive Benefit (Pi) – what the individual gets out of an action plus the benefits to family members

Personal Cost (C) – the price an individual pays for an action

Inclusive Cost (Ci) – the price an individual pays plus the price to family members

  1. Operational Altruism P < C

An observer sees the short-term cost to the altruist exceeding the short-term payoff to the altruist. This perception is what biologists wish to explain.

  1. True Altruism Pi < Ci

Actual inclusive cost exceeds inclusive personal reward. Note that neither intention nor actual benefit to other is required. In kin selection Case 1 applies and Case 2 does not.

  1. “Ethical” Altruism actor intends Pi < Ci

Willed inclusive cost exceeds willed inclusive reward. Note that no actual benefit to self or other is calculated. Only intention matters. This may be adaptive if Case 3 leads to Case 1, but not Case 2. In other words, your conscious state must affect your behavior in order for ethical altruism to have effects in evolutionary biology. You cannot deny free will AND claim that ethical altruism is a product of natural selection.

  1. Theological Altruism Cases 2 and 3 together

Personal sacrifice and benefit to other are both intended and achieved. Theological altruism here suggests that something is independently justified, both as means and as ends. You are willing to help at cost to self and you manage to do so. Note that future rewards can void theological altruism so constructed.

  1. Signaled Altruism causing the appearance of Case 1

Giving the signal that you are altruistic may be beneficial in creating relationships independent of whether Cases 1 and 2 objectively apply.  It does not matter here whether the signal is true or a lie. Biologists speak of costly signaling, when an individual invests substantially in an interaction (mating, community membership), demonstrating wealth (extra resources to spend – e.g., Peacock’s tail) or commitment (inability to back out of a deal – e.g., giving up technology to join the Amish). Such signals can be faked. Because costly signals can be associated with joining a group of mutual aid, fake signals represent a common strategy for taking advantage of the group – free riding. This is not to suggest that free riders are common, only that among free riders, fake signals are common.

  1. Adapted Altruism Case 1 plus long-term average NOT Case 2

Past events have led to personal sacrifice beneficial to the long-term interests of self (as gene or lineage [or debatably] population). Group, inter-deme, and kin selection as well as reciprocal altruism fall into Case 6.

Biological Altruism can refer to any biological explanation of Case 1. Generally, these will be adaptive (Case 6) explanations, but others exist as well. Gould’s spandrels (non-adaptive traits coming in on the coat-tails of adaptive traits) and parasitism (adaptive for someone, but not the altruist) come to mind. It’s important to note that natural selection favors parasitism in a very limited way. The parasite’s behavior will tend to be optimized for taking advantage, but the host’s behavior will be optimized for resisting. It’s important to calculate cost and benefit for all parties and watch how the environment shapes each.


We spent most of the discussion speaking about the ethical implications of in-group favoritism and reciprocity. How do we think and feel about moral decisions made for the sake of a community, but at the expense of others? How do we think and feel about conscious manipulation of other people’s unconscious behavioral responses to stimuli? (See Influence by Cialdini and Nudge by Sustein and Thaler)

Issues of inclusive versus exclusive costs and benefits raise a number of social morality questions for theologians as well as biologists. Likewise, thoughts about intention, result, and signalling reveal a great deal about the way we negotiate social interactions and bear further reflection at a number of levels. We discussed the case of inexpensive gifts (paying for dinner on a first date, accepting a flower or book from a Jehovah’s Witness). Should they be accepted? Should they be offered? And how should they be viewed, morally? Do the answers change as a function of how aware giver and receiver are of behavioral economics, game theory, and evolutionary biology?


Meeting 4.2 – Human Exceptionalism

On 23 February the reading group met for the second time.  We discussed human exceptionalism – whether and how humans might be different from other animals.

We began our discussion by talking about concrete questions: Can humans do things other organisms cannot? Should we treat humans differently?

Do humans have any unique faculties? Would we be able to verify them empirically and consistently? In general, we concluded that there is benefit to treating humans as animals in order to study them scientifically, but that this might not be the only way to study humans. As far as biology is concerned, human traits are, at most, complex versions of traits found in other species.

Do humans deserve special treatment? Why treat humans well? Why treat all humans well? Why give humans preference over other things? This has profound implications for the rights and obligations we assign to humans as well as the individuals we consider human.

A third aspect is related to both and has to do with relationships and whether humans faculties and dignities arise from our social interactions and interaction with God.

Human exceptionalism usually goes with ideas of human superiority, but there is no logical reason it must. Note that humans are almost always classed as rational animals historically.

Soul and spirit and their Latin and Greek cognates come from the idea of movement.

Spirit, ruach, pneuma, spiritus, pneumatic, inspiration (breath, geist, ghost)

Soul, nephesh, phsyche, anima, animate, animal, psychology

[“Life” comes from the same Germanic root as “leave” and means to persist.]

[“Mind” comes from the Germanic for intellect – though Descartes used “anima.”]


Human exceptionalism has played a large role in debates over evolution.

1. Non-exceptionalists claim humans are just another animal. What work is done by the word “just”? (TH Huxley, JBS Haldane, SJ Gould)

2. Progressive exceptionalists claim humans developed or emerged (Darwin, AR Wallace, T de Chardin, T Dobzhansky)

3. Eternal exceptionalists claim humans are, by nature, different (Aristotle, Louis Agassiz, possibly C Linnaeus)

4. Inserted exceptionalists claim something was added to humans either once or individually – soul creationism (AH Strong, CS Lewis)

“The wine in the miracle was not water because water had been used in the making of it, nor is man a brute because the brute has made some contributions to its creation.” -AH Strong (Systematic Theology 1885)

An important question must be: exceptional in what regard?

And who was exceptional, exactly? In South Carolina, evolution was unfavorable because it suggested white and black humans were related. In New Zealand, it was favorable because it suggested white humans had outcompeted the Maori.


Murphy, Nancy (2006) Bodies and Souls, or Spirited Bodies. (Cambridge: Current Issues in Theology). pp.1-37. (Chapter 1)

What is a human/person at the most basic level? The formal study of this question in Christian theology is called Theological Anthropology.

The Ontological Question asks how many parts humans have.

1. Monism: Humans have only one part. It could be physicalism (only body) or idealism (only mind or soul).

2. Dualism: Humans have two components that differ in the way they exist. Different people have constructed this differntly and it is important not to conflate their accounts.

Plato: eternal forms are trapped in changeable matter, as prisoners in a jail

Aristotle: all things are informed matter (hylomorphism), containing both parts

Plotinus: perfect forms have become mired in corrupt matter, as animals in a tar pit

Aquinas: spiritual forms and corporeal matter were created separately be God and joined together at conception (and resurrection), as software and hardware (Note that a soul is said to subsist if it can exist independent of the body. Plato thought it good for a soul to subsist. Aquinas thought it possible, but bad. Aristotle arguably thought it impossible.)

Descartes: Minds drive bodies, as a pilot in a ship

3. Trichotism: Humans have three components: Body, Soul, and Spirit (I Thess 5:23)

Christians have debated over the best way to view life after death.

Immortality – the persistence of the soul

Resurrection – the re-incarnation of the soul

The difference most often appears in theories about whether souls can be said to exist and where they reside between death and resurrection. Both purgatory and limbo deal with this question.

Murphy’s thesis: “humans are psychophysical unities.” “Non-reductive physicalism.” Leaning interactionist with an external focus.

What is the difference between internal and external accounts?
For more commentary, see these earlier discussions:


Discussion of human exceptionalism


Discussion of what is intelligence

Do humans deserve unique treatment?

The question of human exceptionalism is not just one of science. Set aside for the moment, questions of natural and supernatural and empiricism. We want humans to treat humans differently than other animals. With very few exceptions (Peter Singer comes to mind) we take for granted the idea that humans warrant special treatment. Thus, we have the concept of human dignity.

Our categories shape our understanding and the category of human does more than empirical work. It does legal, moral, and theological work as well. It impacts our ethics. When we ask about human uniqueness, we are often asking about the rights or responsibilities attached to human life. Why treat humans well? Why give humans preference over other animals in terms of life, liberty, and flourishing? What freedoms do we expect for humans?

Note that these questions cannot be answered in a vacuum. Unlike questions about human faculties or essential character, the treatment question cannot be disentangled from issues of free will and culpability. We cannot claim that liberty is a human right without thinking humans choose effectively, that they have non-deterministic agency. The book Brave New World deals with this well in proposing humans engineered to enjoy their surroundings. There would be no point to liberty that could not be exercised.

[Opponents of free will may point out that we cannot comprehend the details of determined choices and, therefore, must act as though they humans were free even though we know they aren’t. We can be pragmatic libertarians. First, I’m not sure what the point is of believing in something and acting as though it were not true. It strains the definition of belief. Second, it opens the door, ethically, to anyone who claims a new technology for pacifying the masses, something that happens surprisingly often in human history.]

Neither can we speak of human dignity without asking what it is, operationally, we wish to preserve. Is it human life, human autonomy, human happiness and flourishing? Modern questions about the beginning and end of life – abortion, reproductive technologies, euthanasia – have everything to do with how we put bounds on the categories of things deserving of our moral care. Is a fetus human? Does it have dignity? Does it have rights independent of the mother? Do our rights to autonomy and happiness trump our right to be alive? Do they ever trump the right of another to be alive?

Within the last two centuries, we have seen a gradual shift in thinking to make the category of “human” bigger. There was considerable debate about whether sex and race might affect our rights to life, property, autonomy, and speech. This was not just a question of who gets to be involved in public life; it was a question of what we counted as a “who” in the first place. Moving the border between humans and non-humans has concretely changed politics, economics, and governance within the past hundred years

We still argue over whether our autonomy leads to our dignity or our dignity justifies our autonomy. In the first case, you get rights because you can choose, but if you lose the ability to choose (e.g., a coma) or act in a way that demonstrates unacceptable choices (i.e., crime or immorality, your dignity can be taken away. [This is why I will never be a preference utilitarian or even a Kantian.] In the second case, you are allowed to make choices because of some inherent or essential character of humans. It doesn’t work well with science, but it gets you much closer to what we think of as “human rights.”

There is more I could say (and more I have said here and here), but for now, I simply want to highlight the importance, even the necessity of distinguishing humans from other animals for ethical reasons.

Are There Things Only Humans Can Do?

As part of a recent discussion on human exceptionalism, I put some thought into the question of human uniqueness and what science has to say about the peculiarity of humans. Our first tack was to brainstorm potentially unique human faculties.  Here are my notes.

Human faculties are either activities (processes in action) or abilities (potential processes) considered to be present in humans – potentially exclusively.

Some philosophers have claimed reason, awareness, mind, and intelligence as uniquely human. I worry that these traits are equivalent to, rather than descriptive of, humanity in much of the literature. Insofar as we define them more specifically, we find them in other organisms. Abstract problem solving appears in crows and dolphins and, interestingly, amoebae. Self-recognition appears in elephants, apes, dolphins, and magpies. Synthetic abstraction (combining abstract concepts mentally) appears in dolphins.

A second category of faculties includes agency (the ability to have done otherwise), will or choice (deciding between options), moral reasoning (thinking and choosing on the basis of value), theological altruism (thinking and choosing in a way that benefits others over self), consciousness (internal awareness), and art-for-art’s sake (as opposed to craft for the sake of utility). This list, while easier to speak of concretely in non-humans, is not open to observation. All the elements involve some internal state. Were non-humans to have these faculties, there would be no way to verify them empirically. If we choose them as the dividing line between humans and non-humans, we will need to rely on some other way of knowing (revelation? deduction? tradition?).

A third category contains faculties both specific and potentially empirical). In each case, it has been difficult to stipulate a qualitative difference between human and non-human forms. Humans have complex or “fancy” ways of doing these things. That does not rule them out as functional definitions, but it does mean we’ll need to be careful how we communicate about them. Tool use and transmission has been observed in crows. Agriculture (cultivating plants and fungus as tools) and herding (cultivating animals as tools) have been observed in ants (and here). Evolutionary biologists have, in the past, distinguished artificial selection from natural selection, but it’s unclear on what >empirical< grounds. If the difference is intent or consciousness, then it invokes internal states. If the difference is just that humans do one, then we have not aided our cause of differentiating humans. Many organisms communicate, though humans appear to transmit and rearrange far more complex concepts than other creatures. In particular, we have a rich language and the ability to generate new languages.

In a previous discussion (and here), world-domination was proposed, but cyanobacteria have arguably had a greater impact on the planet than humans, producing the oxygen rich atmosphere (3.5-2.2 billion years ago), killing off most of the other species at the time, and making Earth possible for multicellular organisms (including plants and animals). Along similar lines, we can think of space-exploration. A number of organisms have hitched rides on human spacecraft traveling to the moon and probably beyond (and here). We are also starting to think more seriously about the possibility that meteorite impacts can eject Earth rocks into space with hibernating microbes capable of colonizing other planets.

My friend, Jack suggested nuclear chemistry (causing fusion and fission reactions), which looks promising. While numerous species utilize fusion products (heat and light from the Sun) or colonize radioactive zones (and here), only humans produce nuclear energy and waste products.

Meeting 4.1 – Free Will

The reading group on Biology and Theology met for the first time (for Spring 2015) on 16 February 2015 and talked about free will as it relates to physics and biology. Here are my notes.


Burkeman, Oliver (2015) Why can’t the world’s greatest minds solve the mystery of consciousness? The Guardian (online)

Consciousness is about internal awareness
Qualia – the experience of phenomena through your senses
Reason – the experience of processing information
Choice – the experience of determining an outcome

The Platonic approach to modeling the world starts with qualia and uses reason to justify the existence of external objects. [These are probability arguments] “Noumena” > phenomena > mind
“I think; therefore I am.” –Descartes
“I think I exist. If I’m wrong, who’s mistaken?” –Augustine
The Aristotelian approach starts by assuming that external objects exist and attempts to explain qualia. [These are likelihood arguments] Objects à sense data à “consciousness”

The Ontological Question: what exists?
1) Reductionist Monism: only physical substances exist (Hobbes). OR only mental substances exist (Mary Baker Eddy)
2) Open Monism: only one type of substance exists, but not all substances are captured by the categories “physical”, “mental”, etc. (Gassendi)
3) Dualism: both physical and mental substances exist and follow different laws

The Causal Question: how do they interact?
1) Parallelism: mental and objective events coincide but have no causal interaction (Leibniz)
2) Interactionism: each can affect the other (Descartes) “processor” “vehicle”
3) Epiphenomenalism: objects effect consciousness (TH Huxley) “steam whistle”
4)   Solipsism: mind effects phenomena

Note natural selection only applies for causal interactionism. But causal interactionism appears to defy causal closure. Thus science does not give us unequivocal preference.

The real problem is exclusivism – what is sufficient to explain what we experience? At the heart of the qualia problem is this very issue: how can you say what is sufficient to explain my experience? But there is also a social question: what do we as community X (scientists, philosophers, ethicists, theologians, etc.) judge sufficient?

We also have to deal with miscommunication around the words themselves. Monist physicalists insist on physical interpretations for concepts like preference and choice. Dualists insist the words capture a non-physical reality.


Baumeister, Roy F., Masicampo, E. J., and Vohs Kathleen D. (2011) “Do Conscious Thoughts Cause Behavior?” Annual Review of Psychology 62:331–61.

What is the relationship between conscious information processing, unconscious information processing, and behavior?

Physical Determinism: the now unpopular scientific idea that the future state of a system may be predicted without error given a complete understanding of the current state.

Physical Stochasticity: the scientific idea that the future state of a system may be analyzed using statistics, but may not be precisely predicted.

Skepticism: future states may not be predicted.

Philosophical Determinism: human behavior is fully determined by environmental and historical stimuli.

Agency: “the ability to have done otherwise” – uncaused causal ability. Multiple potential outcomes exist and the agent acts to direct reality down one path or the other. May be conscious or unconscious.

Will: the faculty of choice – may be agential or not, admits of various constraints.

One can be a determinist in either sense (Agency/Will), both, or neither.

Research is showing that will is far more constrained than previously believed and that the conscious experience of choosing can occur after the choice has been made. Mental states appear to affect behavior (anticipated and imagined futures, organizing past events, focus on concrete solutions, cognitive load, explaining, value quotas). Consciousness may be central in modeling the processing of other processors.
Research is showing that conscious processes are clearly integrated with response to stimulus, particularly with regard to behavior across time, social interaction, and prospect and problem solving.

Discussion focused on where the boundaries were and who believed what. Frequently we ran into imported value judgments – why it is “better” to believe or act in certain ways. We agreed that the moral consequences were significant and speculated on the role of human exceptionalism in the construction of all the categories.

For a longer discussion of these topics: and search “free will”2

Religion and Biology Reading List, Spring 2015

This spring the reading group at Harvard continues with a more general focus: issues in biology and theology.  Here is the reading list.

Reading Group on Evolutionary Biology and Theology, Spring 2015

Alternate Mondays 3:30-5:00pm, 4th floor Botany Labs common room (above the glass flowers in the Harvard Museum of Natural History).


16 February: Free Will

To what extent are human actions constrained by history and environment? What aspects of behavior can be predicted through neurology, evolutionary psychology, and behavioral economics? What religious concepts rely on some notion of free will?

Baumeister, R.F., Masicampo, E. J., and Vohs K. D. (2011) “Do Conscious Thoughts Cause Behavior?” Annual Review of Psychology 62:331–61.

Burkeman, Oliver (2015) Why can’t the world’s greatest minds solve the mystery of consciousness? The Guardian (online)


23 February: Human Exceptionalism

Humans have traditionally been classed as animals in biology and theology. Disagreement has arisen in the last few centuries over whether we should think of them as just animals. How does this disagreement impact ethics, science, and public reception of science? What work do religious and ethical differentiations do?

Murphy, Nancy (2006) Bodies and Souls, or Spirited Bodies. (Cambridge: Current Issues in Theology). pp.1-37. (Chapter 1)


9 March: Altruism

What is the relationship between biological altruism and religious concepts of altruism? Can biology explain “selfless” behavior? Can ideas in science and religion promote and discourage “selfless” behavior?

Discussion from Forum on Chance, Purpose, and Progress on types of altruism


23 March: Randomness

What role do concepts of probability, stochasticity, and purposelessness play in evolutionary biology? What religious concepts rely on some notion of purpose, and are they incompatible with biological concepts? How does the general public interpret both?

Barbour, Ian (2000) When science meets religion. Harper. Chapter 3: The Implications of Quantum Physics.


6 April: Life and Death

How are concepts of life and death constructed in biology and how do they impact research? How are concepts of life and death constructed theologically and how do they impact religious thought and practice? What civil/secular/legal concepts of life and death exist and how are they related to scientific and religious concepts?

Mix, Lucas (manuscript) What’s at stake in questions of life and death?


20 April: TBD

(Origin of Life or group selected topic)


Aristotle’s Animal Souls

Aristotle thought of souls as forms travelling through time, both as patterns in space and a chemical process of self-maintenance. Thus they were efficient cause (instigator), formal cause (essence), and final cause (end) for living beings (for more on causes…). They repurposed matter to their own ends in a process called nutrition, but nutrition was not possible forever (think second law of thermodynamics or, if you prefer, recall Aristotle’s belief that all material things must decay). With a goal of eternal persistence, they reproduced, making new copies that could survive after they were gone. All souls behaved this way and all living things had this kind of soul – a vegetable soul.

Though all souls do these things, some souls had other properties as well, higher functions, if you will. Animals were those living things that responded to stimuli and made changes in the world around them. While I find Aristotle’s notion of vegetable souls reconcilable with modern science, I am less hopeful for the animal soul. It requires some different physics than we are used to.

Aristotle believed that forms could be acquired by souls as well as matter. This is somewhat problematic. When a soul acquires new matter (eats) that matter loses its old form and takes on a new one – the soul is both form and activity of adding matter to the form. When a soul acquires a new form, it does not give its matter to that form. Rather, it sequesters the form in a sense organ. Recall that form cannot exist without matter for Aristotle, so external forms are brought to the senses, where an image is “formed.” Debate persists on how this happens. The most literal commentators think that matter in the sense organ takes on the form (as in the liquid in the eye becoming green when it “sees” green). A more common-sense approach suggests that somehow souls receive forms in a symbolic or representative way. The form is taken in as a computer processor takes in file.

This sensation (or acquisition of forms) allows the souls of animals to interact with their environment. They not only input forms, they process them. They prefer some inputs to others and act to change the world according to their preferences. It’s not too difficult to see the parallel with nutrition. Forms are a necessary substrate for perceiving the world. Chase the prey. Flee the predator. Go around the rock. “Prey”, “predator”, and “rock” are all concepts, forms for Aristotle. The animal soul grows and perpetuates itself by acquiring the specific forms of the things around it. Just as we live in the vegetable sense by processing matter and energy from food, so we live in the animal sense by processing forms and relationships from our sensed environment.

Motion is intimately related to sensation, for our choosing means we have favored one form over another, selecting what to chase, what to flee, and what to avoid. For Aristotle, the animal soul is all about stimulus and response. He believed animals had the ability to change their environment in a way that vegetables and rocks could not.

Modern Animals

When it comes to vegetable souls and powers of nutrition and reproduction, they map easily onto modern concepts in modern biology. All organisms repurpose matter to suit their ends and all living things make copies of themselves. This applies not only to vegetables, but protists, bacteria, archaebacteria, … arguably even viruses. When it comes to animal souls we have a harder time.

First, Aristotle’s animals do not correspond well to any modern categories. All organisms respond to stimuli. Plants are far more active than we once thought. Starting in the 1970s biologists began to recognize the complex biochemical senses and actions of plants. Some plants even move, like the Venus flytrap. Bacteria and other one-celled organisms can also move and respond to stimuli. So, if we were to apply Aristotle’s animal souls, we would have to apply them to just about every form of Earth life. Viruses would be debatable, though we debate about them anyway, so that’s less of a problem.

Second, we no longer have a clear concept of forms; it would be hard to say what the acquisition of forms means to a modern listener. Until very recently, most thinkers thought that thinking (and perceiving) required the things thought about to exist somewhere. Now we know that computers (and fungus) can solve problems purely algorithmically, following steps without ever conceiving of the problem or even the components. They respond automatically. Perhaps humans also solve problems automatically and our “concepts” are not involved. Instead they might just be our attempt to understand what we’ve done, after the fact. (For more on this problem of will and consciousness, check out this discussion I led a the University of Arizona.)

For Aristotle, there was a clear line between sensing moving things (animals) and all other living things (vegetables). The animal soul represents the active power and end of perceiving that enlivens animals, allowing them to sense, choose, and act in the world. It was not a second soul, added to the vegetable soul, but a single soul that encompassed both activities. It may not be useful to us today, but it gives great insight into how Aristotle thought and how philosophers approached questions of life through the ages.