A Brief Introduction to Hume's Is/Ought Problem

In the mid eighteenth century, David Hume, a Scottish Enlightenment philosopher and champion of modern secularists, laid out what was called the Is-Ought Problem in his A Treatise of Human Nature.  I will quote his description of the problem in that text:

In every system of morality, which I have hitherto met with, I have always remark’d, that the author proceeds for some time in the ordinary way of reasoning, and establishes the being of a God, or makes observations concerning human affairs; when of a sudden I am surpriz’d to find, that instead of the usual copulations of propositions, is, and is not, I meet with no proposition that is not connected with an ought, or an ought not. This change is imperceptible; but is, however, of the last consequence. For as this ought, or ought not, expresses some new relation or affirmation, ’tis necessary that it shou’d be observ’d and explain’d; and at the same time that a reason should be given, for what seems altogether inconceivable, how this new relation can be a deduction from others, which are entirely different from it. But as authors do not commonly use this precaution, I shall presume to recommend it to the readers; and am persuaded, that this small attention wou’d subvert all the vulgar systems of morality, and let us see, that the distinction of vice and virtue is not founded merely on the relations of objects, nor is perceiv’d by reason.[1]   

This is called the Is-Ought Problem, because Hume argued that one cannot reason from premises which are only statements about what is the case, to statements about what ought to be the case.  He was responding to the Enlightenment philosophers who sought to rationally ground morality in a number of different ways.  Noting that these is-propositions and those ought-propositions are different in structure, he observed that these produce syllogisms which are not logically valid.  Here are some examples of the sort of arguments to which Hume was referring:

1. Calling Hermione a Mudblood will cause her emotional pain.
2. Therefore I ought not call Hermione a mudblood.

Or:

1. I wouldn't like it if the opposing quarterback partially deflated his footballs before an NFL game to gain a competitive edge.
2. Therefore, I ought not deflate my own footballs before an NFL game to gain a competitive edge.[2]

You can easily see that each of these syllogisms is invalid and possibly incomplete as they are currently written out, for the reasons that Hume gave.  In a following post, I will consider how Alasdair MacIntyre responds to this "problem" by invoking the pre-modern understanding of function and how it relates to the virtues.

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Notes:

1.  Hume, 1739

2.  I thought it worth mentioning that I chose these two examples because they reflect real attempts of Enlightenment philosophers to ground morals in reason.  The first (about Hermione) reflects the Utilitarian tendencies of Jeremy Bentham and John Stuart Mill to ground morality in pain and pleasure.  The second (about Tom Brady) reflects the Universality measure that Kant employed to justify morality (any moral imperative must apply equally to every person universally).