 Because our concern will be with voluntary euthanasia – that is, with those instances of euthanasia in which a clearly competent person makes a voluntary and enduring request to be helped to die (or, by extension, when an authorised proxy makes a substituted judgment by choosing in the manner the no-longer-competent person would have chosen had he remained competent) – a second key value is the competence of the person requesting assistance with dying. There will be occasion to mention non-voluntary euthanasia – instances of euthanasia where a person lacks the competence at the time when a decision is to be made to request euthanasia and has not previously competently declared a preference for it via an advance directive (see the entry on  advance directives)  – only when consideration is given to the claim that permitting voluntary euthanasia will lead via a slippery slope to permitting non-voluntary euthanasia. Nothing will be said here about involuntary euthanasia, where a competent person’s life is brought to an end despite an explicit expression of opposition to euthanasia, beyond saying that, no matter how honorable the perpetrator’s motive, such a death is, and ought to be, unlawful.