A Humean theory of choice of which rationality may be one consequence

Abstract

For the reader who considers economic theory of choice as a special case of a more general theory of action, Hume's discussion of the determinants of action in the Treatise of Human Nature (1739 – 40), in the Enquiry on Human Understanding (1748) and in the Dissertation on Passions (1757) deserves attention. However, according to some modern commentators, Hume does not seem to have given any evidence that would favour what nowadays we would consider as the kind of rationality involved in modern theories of rational choice. On the contrary, this paper arrives at the conclusion that consistency between preferences and choice, like the usual properties of completeness and transitivity, may be considered as outcomes of a mental process, described by means of a decision algorithm that aims to represent Hume's theory of choice.

Keywords:

• Hume
• rationality
• decision
• passion
• desire
• preference
• will
• choice

Notes

See Hume 1739 – 40, II, part 3, section 3: ‘On the influencing motives of the will’.

As a result of a lack of discrimination, Luce (1956), for instance, constructed the concept of ‘semi-order’, in which strict preferences are transitive but indifference is not necessarily transitive – which means that R is quasi-transitive.

For the definition of WARP, see infra, note 20.

In D. Davidson's words, Hume has a propositional theory of pride, which concerns the fact of being proud of something, instead of being a proud person (Davidson 1976). (See also Árdal 1966: 16 sqq, and 1989.)

Hume's taxonomy of indirect passions is based on a double criterion: the object might be either ‘self’ (pride and humility) or ‘another’ (love and hatred); the associate sensation might be either ‘agreeable’ (pride and love) or ‘disagreeable’ (humility and hatred). This taxonomy is conceived in such a way that all other indirect passions (ambition, vanity, envy, pity, malice, generosity…) appear as variants of the first ones.

More precisely, Hume argues that ‘[t]he only existences, of which we are certain, are perceptions, which being immediately present to us by consciousness, command our strongest assent’ (Hume 1739 – 40, I: 212).

Although the perspective adopted here is quite different, such a way to consider that preferences do not exist prior to the choice situation but are constructed within the decision process, should not be surprising to those who are familiar to the works of psychologists on preferences and choice. (See, for example, Tversky 1996.)

This enumeration leaves aside the ‘mixed’ passions of hope and fear, which appear as immediately linked to the question of choice in uncertainty (see Lapidus 2000: 51 sqq).

‘[G]ood and evil, or in other words, pain and pleasure […]’ (Hume 1739 – 40, II: 439).

See, for example, Hume 1739 – 40, I: 119. The force of an idea of an impression is what Hume calls the ‘belief’ in this impression.

From another point of view, it should be noted that since desires refer, as ‘impressions of reflection’, to either pain or pleasure, they supply something more than preferences. They assume the existence of some kind of zero-value, which separates aversion and desire, and which is lacking in the usual conception of preferences. This makes significant the fact that some combinations of objects might be at the border between desire and aversion. In spite of its importance for the rest of Hume's construction, this dimension of desire and aversion will be neglected hereafter.

Garrett (1997: 250 n. 10) nonetheless mentions the possibility to generalize Hume's approach to relations of an order greater than two.

In the enthusiasm of the Abstract, Hume concludes that the natural relations ‘are really, to us, the cement of the universe, and all the operations of the mind must, in a great measure, depend on them’ (Hume 1740: 662).

Nonetheless, resemblance, contiguity and causality are considered as natural relations when they associate (Hume 1739 – 40, I: 10 – 3; 92 – 3), and as philosophical relations when they compare (ibid.: 69 – 78).

The principle of the ‘double relation’ is analysed in detail in Book II of the Treatise (Hume 1739 – 40, II: 282 – 4), where it is mentioned repeatedly (for example, ibid.: 438 – 9) before being reminded again in Book III (Hume 1739 – 40, III: 574).

Hume notes that ‘there is an attraction or association among impressions, as well as among ideas; tho’ with this remarkable difference, that ideas are associated by resemblance, contiguity, and causation; and impressions only by resemblance’ (Hume 1739 – 40, II: 283).

In the case of intertemporal preferences, Hume's argument concerns the increase of the preference for the present, which corresponds to the transformation of a ‘calm’ passion into a ‘violent’ one, as a result of an enhanced efficiency of the natural relation of contiguity (see Lapidus 2000: 45 – 9).

A ‘rationalizing profile’ over F is a profile Π = (…, R_S, …) of binary relations over S ∈ F, such that ∀ S ∈ F, C(S) = {x ∈ S : x R_S y, ∀ y ∈ S}. (See Diaye 2001.)

Obviously, the resulting preferences R_Xn are path-dependent, just like for Hume, a passionate state would depend on a passionate path.

• There are various versions of these well-known axioms. However, they can be stated as follows:

  	1.	WARP: ∀ x, y ∈ Xn, xKy ⇒ ¬ yμx,
  	2.	SARP: ∀ x, y ∈ Xn, xK*y ⇒ ¬ yμx,

• where:

  	1.	K is defined by ∀ x, y ∈ Xn, xKy ⇔ ∃ S ∈ Fn: x ∈ C(S) and y ∈ S\C(S);
  	2.	K* is the transitive closure of K;
  	3.	and μ is the revealed preference relation, defined by ∀ x, y ∈ Xn, yμx ⇔ ∃ S’ ∈ Fn, y ∈ C(S’) and x ∈ S’.