Consequentialist moral theories are often criticized for the degree of personal sacrifice they seem to require, on the part of some, in order to improve the lives of others. Life-changing self-sacrifice, it is often thought, may be laudable, but it is not morally required. Tim Mulgan believes that this ‘demandingness’ objection has force against many forms of consequentialism, but that it is possible to develop a consequentialist moral theory that answers this objection and, moreover, is superior, all things considered, to the currently prominent consequentialist moral theories.

Mulgan calls his theory ‘Combined Consequentialism’, because it is a combination of several different consequentialist theoretical structures. The components of Combined Consequentialism are based on the concept of the moral community – those of us who are ‘comparatively equal moral agents who can interact in mutually advantageous ways in pursuit of their goals’ – which in turn informs the distinction between two ‘realms of moral choice’ (p. 172). In the realm of necessity, active members of the moral community decide whether to enable those excluded from the moral community to participate in it (such as by meeting their most urgent needs); and in the realm of reciprocity, active members of the moral community decide how to interact with one another, more in the pursuit of their respective goals than in the meeting of needs (p. 172). When we face decisions within the realm of necessity, an act-consequentialist maximization of overall good is the correct approach. But in the realm of reciprocity, a rule-consequentialist theory, such as that advocated by Brad Hooker, is more appropriate. In addition, Mulgan says the competing demands of the two realms are appropriately balanced by a modified version of Samuel Scheffler's hybrid view (p. 260). On Scheffler's original view, the act-consequentialist requirement to maximize the good is mitigated by an agent-centred prerogative that permits each agent to multiply his or her interests by some constant, to give them extra weight in the weighing of interests; Mulgan modifies this by replacing the constant with a variable, so that ‘As the cost the agent must bear to produce a given amount of good increases, the weight she is allowed to give to her own interests also increases’ (p. 268). Although the three components of the view are reasonably clear, how they work together – in particular, how the modified hybrid view ‘balances’ the demands of the other two – is not entirely evident, since Mulgan never articulates a principle of the form ‘An act is right if and only if. . .’ or provides, in some other comparably explicit way, necessary and sufficient conditions for right action. Nevertheless, the three main parts of Combined Consequentialism are developed unambiguously and thoroughly.

Mulgan arrives at his view by examining different forms of consequentialism, presenting objections to each one, and then recovering those parts of rejected theories (with some modifications, such as in the case of Scheffler's agent-centred prerogative) that he wants to incorporate into his own view. Along the way, there emerge a number of key assumptions that some readers may want to question. First, as noted, Mulgan divides people into those who are part of the moral community and those who are not (p. 255); but surely the reality of this, as found in the six billion people of our world, is more of a continuum than a dichotomy, and it is not clear how Mulgan's framework of two realms can be adapted to this fact. Second, Mulgan defends his modification of Scheffler's agent-centred prerogative by asserting that ‘where two agents are in some sense giving up the same amount of well-being, the one who was worse off to start with is making a greater sacrifice’ (pp. 272–3). Of course, it is often said that when two agents are giving up the same amount of resources such as money, food and shelter, then the one who is worse off to start with is making a greater sacrifice; that is, most resources are often thought to exhibit diminishing marginal utility. But well-being, in contrast, is generally understood as equivalent to utility, so that Mulgan's claim seems akin to asserting the diminishing marginal utility of utility. Presumably this is a misreading of Mulgan's text rather than an internal contradiction on his part, but how to avoid it is not apparent from Mulgan's too-brief account of this important ‘deeper rationale’ (p. 272) for his modification of Scheffler's view.

Third, Mulgan criticizes prominent forms of consequentialism, and defends his own theory, largely by relying on certain intuitions about how demanding it is reasonable for a moral theory to be. Comparatively little attention is paid to intuitions on other topics than demandingness, and little justification is offered for relying so heavily on intuitions at all. Additionally, Mulgan's intuitions about demandingness are not explicitly laid out in advance; we just learn along the way that the demands of certain outlooks are excessive, that those of others (such as common-sense morality) are deficient (p. 291), and so on. The method of appealing to intuition may be nearly inescapable in moral theory, but the way Mulgan employs it might not resonate with all readers. Finally, the way in which Mulgan's own theory consists of three disparate parts runs the risk of seeming ad hoc rather than genuinely illuminating about the theoretical structure of morality – especially if one holds the assumption that in order for systematic moral theorizing to be preferable to particularism, then a proposed theory should have a fairly simple unifying idea. (For Mulgan, consequentialism itself is the unifying idea, and then conflicting expressions of that idea can figure in one's theory in different ways.)

Although Mulgan makes a number of controversial assumptions, he takes advantage of the latitude they offer to develop a rich and nuanced theory. The theory is not developed concisely; at about 125,000 words, this book is about twice as long as each of the two books that provide most of the key ingredients for it – namely, Scheffler's The Rejection of Consequentialism (1982) and Hooker's Ideal Code, Real World: A Rule-consequentialist Theory of Morality (2000). What these works accomplish in a small space suggests that Combined Consequentialism might have lent itself to a similarly compact presentation. Nevertheless, The Demands of Consequentialism is a formidable achievement, and is an original contribution to consequentialist thinking about morality.