• Donation/Procurement of Organs/Tissues
• Ethics
• Informed Consent
• Political Philosophy

Douglas MacKay has recently argued that opt-out organ procurement systems are not sufficiently respectful of people's autonomy (D MacKay. Opt-out and consent. J Med Ethics forthcoming). One of his targets is a paper of mine in this journal.1 Here, I reply to some of his criticisms.

First, let me summarise my position. I argued that an opt-out system of organ procurement should not be identified with ‘presumed consent’ because various (putative) justifications are available for such a system (ref. 1, p. 69). I then proposed that an opt-out system can be understood as relying on tacit consent (ref. 1, p. 70). Since there is no ‘natural’ act of consent, the state can specify various acts and procedures, such as carrying a donor card or signing up to a register (ref. 1, p. 71). One possibility is to decree that consent is given by the act of not registering one's objection (opting out). I note that certain background conditions—principally widespread public awareness of the system—are necessary for this consent to be valid (ref. 1, pp. 71–2). Nonetheless, consent is not simply presumed, but actually given, although implicitly (ref. 1, p. 71).

MacKay accepts that implicit consent can be valid consent (D MacKay. forthcoming, p. 3). However, he suggests that a further understanding condition is needed. It is useful to distinguish between the weaker claim, that understanding is necessary for valid consent, and the logically stronger claim that understanding is necessary for consent simpliciter. MacKay appears to endorse the latter (D MacKay. forthcoming, p. 3). I reject the strong claim and then question the weaker one.