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Course 14 · Lesson 6.3

Evolution and moral knowledge

10 minute read

Lessons in this course

Course 14 outline

Module 1: Arguments, Existence and Necessity

  1. What natural theology attempts and what it does not
  2. Necessary and contingent existence
  3. How to read and test an argument for God
  4. Philosophy of religion today: a map of the field

Module 2: The Ontological Argument

  1. Anselm and the argument of the Proslogion
  2. Gaunilo and the perfect island objection
  3. Kant: existence is not a real predicate
  4. What the ontological argument would show if it worked

Module 3: Cosmological Arguments

  1. Aquinas: the first three ways
  2. Infinite regress: what is the problem?
  3. Leibniz, the principle of sufficient reason and the argument from contingency
  4. Objections: the brute fact reply and the fallacy of composition

Module 4: The Kalam Cosmological Argument

  1. The kalam tradition: Philoponus, al-Ghazali and Bonaventure
  2. The modern argument: whatever begins to exist has a cause
  3. Did the universe begin? Philosophy and cosmology
  4. Objections and replies, and what follows about the cause

Module 5: Teleological and Fine-Tuning Arguments

  1. From Aquinas’s fifth way to Paley’s watch
  2. Hume and the Dialogues Concerning Natural Religion
  3. Darwin and the change in the design argument
  4. The fine-tuning argument: what is claimed and what is debated
  5. The multiverse and other replies

Module 6: The Moral Argument and Divine Hiddenness

  1. The moral argument: Kant, Lewis and contemporary forms
  2. The Euthyphro question and moral realism without God
  3. Evolution and moral knowledge
  4. The argument from divine hiddenness and Christian replies

Module 7: Contemporary Modal Arguments and Evaluation

  1. Possible worlds and modal logic in plain language
  2. Plantinga’s modal ontological argument
  3. Assessing the modal argument: what it needs and what it shows
  4. Weighing the arguments together, and what none of them prove

All courses

Program / Course 14: Arguments for the Existence of God / Lesson 6.3

What you will learn

  • Explain the evolutionary debunking argument against moral realism.
  • State how defenders of the moral argument use it and how critics reply.
  • Distinguish explaining how moral beliefs arose from showing they are false.
  • Say what questions remain open.

The big idea

If human beings are the product of natural selection, then human moral beliefs were shaped by what helped human ancestors survive and reproduce, not by tracking moral truth. Some philosophers argue that this undercuts confidence in objective morality, unless it comes from a source that aims at truth. Theists sometimes use this to support the moral argument. Critics reply that origins do not decide truth, that moral beliefs could have been shaped to track real moral facts, and that the argument also troubles theists.

Key terms

Evolutionary debunking argument
An argument that a set of beliefs is undermined because the process that produced them did not aim at truth.
Genetic fallacy
The mistake of judging a belief true or false by where it came from, rather than by the reasons for it.
Reliable faculty
A way of forming beliefs that tends to give true ones.
Altruism
Behavior that benefits others at some cost to oneself.
Kin selection and reciprocal altruism
Evolutionary explanations of helping behavior as favoring relatives or those who return help.
Moral intuition
A direct sense that something is right or wrong, not derived from argument.
Evolutionary argument against naturalism
Alvin Plantinga’s argument that if both naturalism and evolution are true, there is reason to doubt that human faculties reliably give true beliefs.

Background

Charles Darwin discussed morality in The Descent of Man (1871) and suggested that moral sentiments arose from social instincts. In the twentieth century, writers such as E. O. Wilson argued that ethics could be explained biologically. Michael Ruse and Wilson claimed that morality is a collective illusion fostered by genes to make people cooperate. Sharon Street’s paper A Darwinian Dilemma for Realist Theories of Value (2006) gave the debunking argument its modern form.

These arguments raise a question for everyone. If natural selection shaped the human moral sense, how can it be trusted? The question has been used both against moral realism and in support of the moral argument for God.

Step-by-step explanation

Step 1: The debunking argument

The argument runs: 1. Natural selection shaped human moral beliefs to promote survival and reproduction. 2. Whether those beliefs are true would make little difference to survival, if there are objective moral facts. 3. So it would be a coincidence if human moral beliefs matched moral truth. 4. So, if realism is true, there is reason to doubt human moral beliefs. Street concluded that realism should be rejected in favor of views in which moral value depends on human attitudes.

Step 2: Use by defenders of the moral argument

Some theists argue that the debunking worry is serious for naturalist realists, who say that moral facts exist but have no connection with natural selection. If instead the world was made by a good God who wanted creatures to know the good, there would be a reason why the human moral sense tracks moral truth. So, on this view, theism better explains moral knowledge. Linville and others have developed this as an argument.

Step 3: Replies from realists

Secular realists reply in several ways. Some, like David Enoch, argue that survival requires acting in accord with what is actually good for creatures, so selection pressure and moral truth could be linked. Others say that human reasoning developed beyond immediate survival and can reflect on and correct moral instincts, as when moral views have changed about slavery. Others say that the argument, if sound, would undermine mathematics and logic too, which are also products of evolution, and they take the conclusion to be too strong.

Step 4: The genetic fallacy objection

Critics say that how a belief arose does not show it false. A person might learn arithmetic in a way shaped by social habits and yet reach true results. To show a belief is unreliable needs more than a story of origin. Defenders of debunking reply that the point is not that origins refute beliefs, but that if the process would produce the same beliefs whether or not they were true, the beliefs lose their support.

Step 5: Does the argument cut against theists?

Skeptics note that believers also accept evolution, usually, and that evolved faculties give them religious beliefs too. If human moral faculties are doubtful because they evolved, so might religious ones be. Theists reply that they hold God guided or permitted the process, which gives reason to trust human faculties. Plantinga has turned the argument on naturalists, saying that if naturalism and evolution are both true, there is reason to doubt all human faculties. Most philosophers do not find this convincing, and the whole matter is debated.

  1. Does learning how a belief arose make you less sure of it?
  2. Is moral progress, such as the end of slavery, evidence that the human moral sense can track truth?
  3. Would a different history have given people a different morality?
  4. Is the debunking argument also a problem for belief in God?
  5. Why might a theist think a good God makes the human moral sense more reliable?
  6. What is the difference between explaining a belief and refuting it?

Examples

A taste for sugar

The human liking for sweet food arose because sugar was a useful, scarce source of energy. That explains the taste but does not make it true that sugar is good for everyone. Debunkers say moral feelings may be like this: useful, but not a guide to truth. Realists say that the analogy fails, since morality involves reasoning and not just taste.

Reflecting on slavery

Most societies once accepted slavery, and later many came to reject it. Realists say this change shows moral reasoning can correct inherited attitudes and move toward truth. Anti-realists say that attitudes can change without moving toward truth. Historians note that Christian conviction played a role in the abolition movement, though Christians were also divided on slavery.

Mathematics and evolution

If evolution makes moral beliefs doubtful, should it do the same for beliefs about numbers? Most people think arithmetic is reliable, though it too arose from minds shaped by selection. Realists use this to argue that a debunking argument proves too much.

Different perspectives

Catholic

Catholic teaching accepts that evolution may explain the origin of the body, and holds that human reason has a real power to know moral truth through natural law. The Church sees conscience as a work of God in the soul, and so does not regard moral knowledge as something merely biological.

Orthodox

Orthodox theology holds that conscience is a gift of God, tied to the image of God in humanity, and also that sin has darkened it. It would regard moral knowledge as both real and in need of healing, not as a purely natural product.

Protestant

Many Protestants accept evolution and affirm moral knowledge through conscience and Scripture. Reformed thinkers note that sin affects moral understanding. Plantinga’s argument against naturalism and Linville’s moral argument are Protestant contributions. Not all Protestants accept evolution.

Scientific and philosophical views

Evolutionary biologists and philosophers such as Street, Ruse, Joyce and Kitcher offer accounts of moral origins. Many do not draw anti-realist conclusions. The question whether evolutionary accounts undermine realism is a lively one in metaethics, with no agreement.

Skeptical views

Skeptics hold that evolutionary explanations of morality show it to be a human construction, and that no further ground is needed. Others, secular realists, hold that the argument fails because evolved creatures can still track moral truth.

Why it matters

Evolutionary accounts of morality are widely known and often misused in both directions. Studying the debunking argument teaches the difference between explaining and refuting, and shows how a scientific theory can bear on philosophical questions without settling them.

Common misunderstandings

Misunderstanding: Evolution proves morality is an illusion.

Correction: Evolution offers an account of how moral sense arose. Whether that makes moral claims false is a philosophical question, and most philosophers do not think it follows.

Misunderstanding: Christians cannot accept an evolutionary account of conscience.

Correction: Many Christians accept it, holding that God works through natural processes.

Misunderstanding: The debunking argument is an argument for God.

Correction: It is used by some theists as a support, but it is mostly an argument in metaethics, and its main users are secular philosophers.

Misunderstanding: Nonbelievers have no basis for trusting their moral sense.

Correction: They offer several, such as reflection, consistency and its fit with human well-being. Whether these succeed is debated.

Knowledge check

State the evolutionary debunking argument.

Natural selection shaped moral beliefs for survival, not for truth. If there are objective moral facts that have no bearing on survival, then a match between human beliefs and those facts would be a coincidence. So if realism is true, there is reason to doubt human moral beliefs. Street concluded that moral realism should be rejected.

How do some theists use it?

They argue that if a good God made the world and wanted creatures to know the good, there is a reason why the human moral sense tracks truth. Naturalist realists lack such a reason. So theism better explains moral knowledge. Critics reply that evolution could link survival to real goods, and that the argument may also trouble belief in God.

What is the genetic fallacy objection?

It says that where a belief came from does not decide whether it is true. Learning arithmetic through social habits does not make its results false. A debunker replies that the point is not origin alone, but that the process would produce the same beliefs whether or not they were true, which removes their support.

Why might the argument also challenge theists?

Religious beliefs and moral faculties are both the products of evolved minds. If origins in survival make moral beliefs doubtful, the same may apply to religious ones. Theists reply that God guided or permitted the process so that faculties could be trusted. This reply is itself contested.

Think it through

  1. Does knowing the history of a belief change how you hold it?
  2. Which moral beliefs of yours seem independent of your upbringing?
  3. Is trust in human faculties something must be assumed?
  4. How would you respond to a friend who says morality is just evolution?

Independent assignment

Origins and truth

In your own notebook, write 350 to 500 words. Choose a belief you hold whose origin you can trace, such as a moral view you learned from family. Describe how it arose, then explain whether that history makes you more or less confident of it, and why. Link your answer to the debunking argument. Do not send this to anyone.

Further study