failing to live up to the expected standard of care. If this can be shown, then the pursuer must also establish that the defender's failure to live up to the expected standard of care ultimately caused the loss (damnum) complained of. Defences under Scots and Roman-Dutch law of delict There is a distinction between defences aimed at the wrongfulness element and defences which serve to exclude fault. Grounds of justification may be described as circumstances which occur typically or regularly in practice, and which indicate conclusively that interference with a person's legally-protected interests is reasonable and therefore lawful. They are practical examples of circumstances justifying a prima fade infringement of a recognised right or interest, according to the fundamental criterion of reasonableness. They are another expression of the legal convictions of the society. Consent to injury, or Volenti non fit injuria, is a full defence; if successful, there is no delict. As a general defence, it can take two forms: consent to a specific harmful act of the defendant; and assumption of the risk of harm connected with the activity of the defendant. There are five requirements for the defence of consent: capacity; knowledge and appreciation of harm; and consent, or free and voluntary assumption of risk. In addition, the consent must not have been socially undesirable—not seduction, or murder for insurance purposes; and the consent must not have been revoked. Necessity is conduct directed at an innocent person as a result of duress or compulsion, or a threat by a third party or an outside force. Private defence (or self-defence) is conduct directed at the person responsible for the duress or compulsion or threat. There is, therefore, an important distinction between the two. In cases of necessity and private defence, the question is this: Under which circumstances would the legal convictions of the community consider it reasonable to inflict harm to prevent it? The test is objective. It requires a balancing of the parties' and of society's interests. The role of the person against whom the defensive conduct is directed is an important factor in determining whether defence or necessity is being pled. An act of necessity is calculated to avert harm by inflicting it on an innocent person, whereas an act of defence is always directed at a wrongdoer. A person acts in "private defence," and therefore lawfully, when he uses force to ward off an unlawful attack