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    Three themes from David Hume and their consequences for contemporary metaethics: The Slavery of Reason Thesis; The Motivation Argument; and Hume’s No-Ought-From-Is thesis.

    This is a paper straddling metaethics (the nature and justification of moral judgements), the history of philosophy and the philosophy of logic. It deals with three themes from the work of David Hume (1711-1776) together with "matters arising" from the Humean agenda:

    • The Slavery of Reason Thesis ("reason is and ought only to be the slave of the passions"). What does this mean? Is the Slavery of Reason Thesis (or something like it) correct? And what (if anything) does this suggest about the nature of ethics?
    • The Motivation (or Influence) Argument:
      1. Morals have an influence on the actions and affections. [Premise]
      2. Reason alone, as we have already proved, can never have any such influence. [Premise]
      3. Morals...cannot be derived from reason
      What exactly is this argument supposed to prove? Does it succeed? If not, is there a decent argument in the neighbourhood that proves something similar? Can it be used to support non-cognitivism, the idea that moral judgements are neither true nor false?
    • Hume's No-Ought-From-Is thesis: "[It] seems altogether inconceivable", says David Hume, "that this new relation or affirmation [ought] can be a deduction from others, which are entirely different from it". What did Hume mean by this? Can you deduce an ought from an is? If not, why not? And what (if anything) does this suggest about the status of moral judgements? We focus on the idea, common in the 18th century, that logic is conservative - that in a valid inference you cannot get out what you haven't put in. In a famous paper the great New Zealand logician Arthur Prior challenged No-Ought-From-Is, along with the concept of conservativeness. We discuss the responses of Pigden, Schurz, Greg Restall and Gillian Russell, who all try to vindicate different versions of No-Ought-From-Is in the face of Prior's counterexamples.

    About this paper

    Paper title No-Ought-From-Is and the Slavery of Reason
    Subject Philosophy
    EFTS 0.15
    Points 18 points
    Teaching period Not offered in 2024 (On campus)
    Domestic Tuition Fees ( NZD ) $981.75
    International Tuition Fees Tuition Fees for international students are elsewhere on this website.
    One 200-level PHIL paper
    PHIL 414
    Recommended Preparation
    PHIL 222
    Schedule C
    Arts and Music
    (i) PHIL222 is the recommended prerequisite. (ii) May not be credited together with PHIL458 passed before 2011.
    The paper is recommended for Philosophy students and for Philosophy, Politics and Economics students, especially those who have done some logic (PHIL 105 or PHIL 222) and have an interest in ethics and the history of philosophy.

    Teaching staff

    Course co-ordinator and lecturer: Associate Professor Charles Pigden

    Paper Structure

    Two 2-hour lecture/seminars per week. The assessment for this paper is 100% internal and is comprised of three essays and an optional in-class presentation.

    Topics covered include:

    • How do the Slavery of Reason Thesis, the Motivation Argument and No-Ought-From-Is fit together in the argument of Treatise 3.1.1?
    • "Reason is and ought only to be the slave of the passions". What does this mean and is it true?
    • The Slavery of Reason Thesis and rationalism
    • The Slavery of Reason Thesis and the error theory
    • The Slavery of Reason Thesis and contemporary metaethics
    • Norms of rationality
    • No-Ought-From-Is (NOFI): logical and semantic autonomy
    • No-Ought-From-Is: its role in Hume's overall argument
    • Hume's NOFI and the concept of deduction in the 18th century
    • NOFI in the 20th century - what's it got to do with non-cognitivism?
    • NOFI, Prior's paradox and Shorter's critique
    • Moral belief and internalism
    • Does the Motivation Argument succeed as an argument for non-cognitivism?


    In-class contributions: attendance, class discussion and sometimes an optional presentation 5%

    Internal assessment: Students will write three essays choosing from a list of topics prepared by the lecturer.

    • First essay (1500-2500 words) 30%
    • Second essay (1500-2500 words) 30%
    • Third Essay (2000-3000 words) 35%

    At least one essay must be on one of the more logical topics.

    Teaching Arrangements

    Two 2-hour lectures/seminars per week, with a short coffee break halfway through.



    • Is, Ought and All That - Themes From Hume (available form uniprint and as pdf from Blackboard).
    • Pigden, Charles ed (2010), Hume on Is and Ought, Palgrave Macmillan.
    • Pigden, Charles ed (2009) Hume on Motivation and Virtue, Houndmills, Basingstoke: Palgrave-Macmillan.*
    • Pigden, Charles ed (2010) Hume on Motivation and Virtue, Houndmills, Basingstoke: Palgrave-Macmillan.*
    • Hume, David (2006) Moral Philosophy, (Sayre-McCord ed), Indianapolis: Hackett.**
    • Hume, David (2007) An Enquiry Concerning Human Understanding, P. Millican ed. Oxford, Oxford University Press.**

    *Note: Copies on reserve in the Library. Draft versions of many of the constituent papers available online.
    **Note: These are useful editions for the purposes of this paper, but good searchable e-texts of Hume's works are widely available online.

    Graduate Attributes Emphasised
    Interdisciplinary perspective, Scholarship, Communication, Critical thinking, Ethics, Self-motivation.
    View more information about Otago's graduate attributes.
    Learning Outcomes

    Students who successfully complete the paper will acquire:

    • A critical understanding of the ideas, theses and themes discussed in this paper
    • Enhanced knowledge of Hume and his relevance to contemporary ethics and moral psychology, plus an enhanced understanding of both formal logic and logical theory
    • Enhanced logical, analytical, communicative and writing skills


    Not offered in 2024

    Teaching method
    This paper is taught On Campus
    Learning management system
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