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Linking Ethics to Moral Psychology: Dual-Process Theories

In the previous lecture, we were mostly concerned with the use of empirical claims about moral psychology within ethical arguments. Now we turn to whether discoveries about moral psychology can be used to undermine ethical arguments from the outside.

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If you are short of time this week, go straight to Greene contra Ethics (Railgun Remix), consider the outline of the argument and the implications. Then review sections associated with any of the premises you are unsure about. Optionally consider Conclusion: Guesses Aren’t Evidence. Done.


In this lecture, we will consider a loose reconstruction of Greene’s argument for the claim (as I put it) that discoveries in moral psychology reveal that not-justified-inferentially premises about particular moral scenarios cannot be used in ethical arguments (Greene, 2014).

If Greene is right, the methods of Foot (see Foot and Trolley Cases: Kant Was Wrong), Kamm (see Singer vs Kamm on Distance) and Thomson (see Thomson’s Other Method of Trolley Cases) are all misguided, along with many other philosophical arguments in ethics.

We will also eventually (but not in this lecture) examine Greene’s further, logically independent contention that his argument supports the application of some kind of broadly consequentialist ethical theory to unfamiliar problems.

Reflective Equilibrium

If the argument introduced in this lecture is correct, it may support an objection to the method of reflective equilibrium when used in an attempt to discover ethical truths (Singer, 2005).

This would be a significant result because reflective equilibrium ‘is the dominant method in moral and political philosophy’ (Knight, 2023). Indeed, according to (Scanlon, 2002, p. 149), reflective equilibrium is ‘the best way of making up one’s mind about moral matters’ and ‘it is the only defensible method: apparent alternatives to it are illusory.’

What is reflective equilibrium? Rawls introduces the idea like this:

‘one may think of moral theory at first [...] as the attempt to describe our moral capacity [...] what is required is a formulation of a set of principles which, when conjoined to our beliefs and knowledge of the circumstances, would lead us to make these judgments with their supporting reasons were we to apply these principles conscientiously and intelligently’ (Rawls, 1999, p. 41; see Singer (1974) for critical discussion).

Roughly, then, the idea is to start with not-justified-inferentially judgements you are, on reflection, inclined to make.[1] And then to consider which principles might be consistent with these judgements. You may drop some of the judgements you start with depending on how well principles can be made to fit them.

Relation to Lecture 06

This lecture does not depend on Lecture 06 (as I anticipate that you may skip one or the other of these lectures) but you may find it helpful to relate the two.

The key contrast is this: in Lecture 06, we were concerned with the use of empirical claims about moral psychology within ethical arguments. We considered attempts to show that moral psychology is relevant to ethics which rely on some philosophers’ approaches being broadly correct. In this lecture, our concern is with whether discoveries in moral psychology can undermine the case for accepting non-empirical premises of ethical arguments from the outside. We will consider attempts to show that moral psychology is relevant to ethics which rely on some philosophers’ approaches being substantially misguided.

To assist in understanding the contrast, a recap may be helpful ...

Recap of Lecture 06

Some arguments for ethical principles rely on noninferentially justified premises about particular moral scenarios. Among these arguments, some are straightforwardly undermined or supported by discoveries in moral psychology (see Foot and Trolley Cases: Kant Was Wrong and Singer vs Kamm on Distance). Other arguments have no straightforward relation to discoveries in moral psychology (see Thomson’s Other Method of Trolley Cases). Further, invoking discoveries about framing effects does not, by itself at least, appear to create significant challenges (see Framing Effects: Emotion and Order of Presentation).

Greene’s argument, if correct, shows that discoveries in moral psychology are, after all, relevant to evaluating Thomson’s argument.

In Lecture 06, we considered framing effects (see Framing Effects: Emotion and Order of Presentation). Greene’s argument requires a deeper understanding of the processes underpinning ethical judgements than do arguments from framing effects.

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loose reconstruction : (of an argument). A reconstruction which prioritises finding a correct argument for a significant conclusion over faithfully representing the argument being reconstructed.
not-justified-inferentially : A claim (or premise, or principle) is not-justified-inferentially if it is not justified in virtue of being inferred from some other claim (or premise, or principle).
Claims made on the basis of perception (That jumper is red, say) are typically not-justified-inferentially.
Why not just say ‘noninferentially justified’? Because that can be read as implying that the claim is justified, noninferentially. Whereas ‘not-justified-inferentially’ does not imply this. Any claim which is not justified at all is thereby not-justified-inferentially.
reflective equilibrium : A method that is supposed to provide justification for claims. The idea is to gather considered judgements about particular situations and attempt to identify principles which from which those judgements could be inferred, and then to adjust the judgements and principles so that they cohere. The canonical statement is Rawls (1999) (but Rawls, 1951 is a useful earlier statement). Authoritative secondary sources are Knight (2023) and Scanlon (2002).
unfamiliar problem : An unfamiliar problem (or situation) is one ‘with which we have inadequate evolutionary, cultural, or personal experience’ (Greene, 2014, p. 714).


Audi, R. (2015). Intuition and Its Place in Ethics. Journal of the American Philosophical Association, 1(1), 57–77.
Greene, J. D. (2014). Beyond Point-and-Shoot Morality: Why Cognitive (Neuro)Science Matters for Ethics. Ethics, 124(4), 695–726.
Knight, C. (2023). Reflective Equilibrium. In E. N. Zalta & U. Nodelman (Eds.), The Stanford Encyclopedia of Philosophy (Winter 2023). Metaphysics Research Lab, Stanford University. Retrieved from
Koenigs, M., Young, L., Adolphs, R., Tranel, D., Cushman, F., Hauser, M., & Damasio, A. (2007). Damage to the prefrontal cortex increases utilitarian moral judgements. Nature; London, 446(7138), 908–911.
McMahan, J. (2013). Moral Intuition. In The Blackwell Guide to Ethical Theory (pp. 103–120). Wiley.
Rawls, J. (1951). Outline of a Decision Procedure for Ethics. The Philosophical Review, 60(2), 177–197.
Rawls, J. (1999). A Theory of Justice (Revised edition). Cambridge, Mass: Harvard University Press.
Scanlon, T. M. (2002). Rawls on justification. In S. Freeman (Ed.), The cambridge companion to rawls (pp. 139–167). Cambridge: Cambridge University Press.
Singer, P. (1974). Sidgwick and Reflective Equilibrium. The Monist, 58(3), 490–517.
Singer, P. (2005). Ethics and Intuitions. The Journal of Ethics, 9(3), 331–352.


  1. Compare Rawls (1951, p. 183): ‘it is required that the judgement [...] not be determined by a systematic and conscious use of ethical principles.’ Rawls goes on to motivate this requirement with the observation that ‘We cannot test a principle honestly by means of judgments wherein it has been consciously and systematically used to determine the decision.’ ↩︎