Negligence liability begins with a duty of care. Its modern form comes from the “neighbour principle”: one must take reasonable care to avoid acts one can reasonably foresee would be likely to injure a person closely and directly affected.
For established categories of relationship, a duty is taken as settled. For novel claims, Canadian courts ask whether the harm was a reasonably foreseeable consequence and whether there was a relationship of proximity, and then whether wider policy reasons should nonetheless negate the duty.
A consumer who fell ill after drinking ginger beer said to contain a decomposed snail could sue the manufacturer despite having no contract with it. The House of Lords recognised a general duty of care in negligence, framed by the 'neighbour principle': one must take reasonable care to avoid acts likely to injure those one can reasonably foresee being affected.