The details of Hume’s moral theory hinge on a distinction between three psychologically distinct players: the moral agent, the receiver, and the moral spectator. The moral agent is the person who performs an action, such as stealing a car; the receiver is the person affected by the conduct, such as the owner of the stolen car; and the moral spectator is the person who observes and, in this case, disapproves of the agent’s action. This agent-receiver-spectator distinction is the product of earlier moral sense theories championed by Anthony Ashley Cooper, better known as the Earl of Shaftesbury (1671-1713), Joseph Butler (1692-1752), and Francis Hutcheson (1694-1747). Most generally, moral sense theories maintained that humans have a faculty of moral perception, similar to our faculties of sensory perception. Just as our external senses detect qualities in external objects, such as colours and shapes, so too does our moral faculty detect good and bad moral qualities in people and actions. The parallel with sense perception is important since it presupposes two distinct players: an external thing, such as an apple, and a spectator who perceives a quality in that thing, such as the colour red. In the case of moral perception, the two distinct players are the agent who performs an action, and the spectator who perceives the virtuous conduct within the agent.
Shaftesbury clearly compares moral judgments with sense perception, and specifically uses the term “spectator” in reference to the role of the perceiver: “The Mind, which is Spectator or Auditor of other Minds, cannot be without its Eye and Ear…” (Inquiry, 1699). In his second Sermon, Butler also compares a spectator’s moral approval to sense perception. Butler argues further, though, that the psychological factors that motivate an agent’s conduct are not identical with the psychological factors of the spectator’s approval: “These principles, propensions, or instincts which lead people to do good [as agents], are approved of by a certain faculty within [as spectators], quite distinct from these propensions [of the agent] themselves”(Fifteen Sermons, 1726, 2).
Hutcheson pushes the parallel between sense perception and moral judgment even further. For Hutcheson, our external senses involve an object that we perceive, such as an apple, and a mental perception that we form in response, such as the visual image of the apple. Similarly, our moral sense involves an object that we perceive, specifically and agent’s benevolent action, and a mental perception in response, specifically a feeling of pleasure. Like Butler, Hutcheson drives a wedge between the psychological factors behind an agent’s benevolent motivation and the spectator’s sense of approval. We see this distinction in the following, particularly in items two and three; we also see in the following that Hutcheson uses the term “agent” in contrast with the role of the moral observer:
These three Things are to be distinguished, 1. The Idea of the external Motion, known first by Sense, and its tendency to the Happiness or Misery of some sensitive Nature, often inferred by Argument or Reason, which on these Subjects, suggests as invariable eternal or necessary Truths as any whatsoever. 2. Apprehension or Opinion of the Affections in the Agent, inferred by our Reason: So far the Idea of an Action represents something external to the Observer, really existing whether he had perceived it or not, and having a real Tendency to certain Ends. 3. The Perception of Approbation or Disapprobation arising in the Observer, according as the Affections of the Agent are apprehended kind in their just Degree, or deficient, or malicious. [Illustrations Upon the Moral Sense, Sect. 4] In addition to articulating the differing roles of the agent and spectator, Hutcheson also focuses on the people affected by the agent’s conduct. For convenience, the term “receiver” may be used to pick out the affected parties. For Hutcheson, our moral sense focuses on how many receivers are beneficially affected by an agent’s conduct. This comes across clearly in a famous passage in which Hutcheson speaks of “the greatest Happiness for the Greatest Numbers”: In comparing the moral Qualitys of Actions, in order to regulate our Election among various Actions propos’d, or to find which of them has the greatest moral Excellency, we are led by our moral Sense of Virtue to judge thus; that in equal Degrees of Happiness, expected to proceed from the Action, the Virtue is in proportion to the Number of Persons to whom the Happiness shall extend; … so that, that Action is best, which procures the greatest Happiness for the greatest numbers; and that, worst, which, in like manner, occasions Misery. [An Inquiry Concerning Moral Good and Evil, 1725, Sect. 3.8] Hutcheson continues noting that, when making moral judgments as a spectator, we should compute the consequences of an agent’s conduct upon others.
Within the context of these moral sense theories, Hume developed his own moral theory, relying on the previously established distinction between the agent, receiver, and spectator. This distinction continued after Hume, as we see in Adam Smith’s Theory of Moral Sentiments (1759). In describing the process of sympathy in the spectator, Smith makes the following statement, which implicitly distinguishes between the roles of the agent, receiver, and spectator:
It is to be observed, however, that, how beneficial soever on the one hand, or how hurtful soever on the other, the actions or intentions of the person who acts may have been to the person who is, if I may say so, acted upon, yet if in the one case there appears to have been no propriety in the motives of the agent, if we cannot enter into the affections which influenced his conduct, we have little sympathy with the gratitude of the person who receives the benefit: or if, in the other case, there appears to have been no impropriety in the motives of the agent, if, on the contrary, the affections which influenced his conduct are such as we must necessarily enter into, we can have no sort of sympathy with the resentment of the person who suffers. [Theory of Moral Sentiments, 2.1.3] Adam Smith was perhaps the last of the great moral theorists directly influenced by the moral sense tradition. However, later 18th and 19th century commentators on moral sense theory clearly understood the differing psychological roles of the agent, receiver, and spectator. For example, John Bruce notes the agent-spectator distinction with respect to Hutcheson’s theory of morality. According to Bruce, Hutcheson “observed, that virtuous actions not only afford complacency to the actor, but excite love and esteem in the spectator, and that vicious actions have opposite tendencies and effects” (Elements of the Science of Ethics, 1786, pp. 68-69). Reid, in summarising Hume’s view of the moral sentiments, also recognises this division: As beauty is not a quality of the object, but a certain feeling of the spectator, so virtue and vice are not qualities in the persons to whom language ascribes them [i.e., agents], but feelings of the spectator. [Essays on the Active Powers of Man, 1788, Essay 5.7] In his discussion of Hume’s moral theory, Thomas Brown gives perhaps the clearest account of the differing roles of the agent and the spectator: In every moral action that can be estimated by us, these two sets of feelings may be taken into account; the feelings of the agent when he meditated and willed the action; and the feelings of the spectator, or of him who calmly contemplates the action at any distance of space or time. [Lectures, 1820, Lect. 77]