Not only are people responsible for the intentional harm they cause (called intentional torts), but their failure to act as a reasonable person would be expected to act in similar circumstances (i.e. "negligence") will also give rise to damages.
Everyone has an ongoing duty to conduct themselves, and manage things under their control, with care as towards other persons. Everybody has a duty to ensure that their actions do not cause harm to others.
Negligence, if it causes injury to another, exposes the tortfeasor to tort or personal injury liability.
Negligence is assessed against an objective standard, having regards to the circumstances and to the standard of care which would reasonably be expected of a reasonable person in similar circumstances. The law looks at what a hypothetical reasonably prudent person might have done in similar circumstances.
For experts selling or offering their services to others on that basis, their standard will be elevated to a similar and qualified expert.
Legal theorists, like Canadian law professor Allen Linden in Canadian Tort Law (Butterworths), have tried to break down what can be a very complex area of the law, into an "ABC rule", as follows:
"A plaintiff in a negligence action is entitled to succeed by establishing three things to the satisfaction of the court: (A) a duty of care exists; (B) there has been a breach of that duty; and (C) damage has resulted from that breach."
In Ryan v The City of Victoria (1999 1 SCR 201), Canada's Supreme Court opined that:
"Conduct is negligent if it creates an objectively unreasonable risk of harm. To avoid liability, a person must exercise the standard of care that would be expected of an ordinary, reasonable and prudent person in the same circumstances. The measure of what is reasonable depends on the facts of each case, including the likelihood of a known or foreseeable harm, the gravity of that harm, and the burden or cost which would be incurred to prevent the injury."
Between negligence and the intentional act there lies yet another, more serious type of negligence which is called gross negligence. Gross negligence is any action or an omission in reckless disregard of the consequences to the safety or property of another. See also contributory negligence and comparative negligence.
Comparatively, Quebec's Civil Code defines negligence in terms of civil liability and as folows, at ¶1457:
"Every person has a duty to abide by the rules of conduct which lie upon him, according to the circumstances, usage or law, so as not to cause injury to another.
"Where he is endowed with reason and fails in this duty, he is responsible for any injury he causes to another person by such fault and is liable to reparation for the injury, whether it be bodily, moral or material in nature.
"He is also liable, in certain cases, to reparation for injury caused to another by the act or fault of another person or by the act of things in his custody."