Negligence determines whether the defendant can be held liable for carelessly causing injury to the plaintiff (ie: manufacture produces beverage that makes consumers sick; investment counsellor"s bad advice leads to client purchasing worthless stocks). Professional negligence is when negligence is committed by a professional person (ie: banker, lawyer, accountant). **note: should establish if they are professional"s first because they have different treatment. Duty of care exists if the defendant is required to use reasonable care to avoid injuring the plaintiff. Without duty of care there cannot be liability, even if the defendant carelessly injured the plaintiff. Test for determining the existence of duty of care. Open the floodgates, encourage people to swamp courts with lawsuits. Hurt a valuable type of relationship (why mother doesn"t owe duty of care. Employee cannot sue an employer in tort for carelessly causing mental distress on job because it would limit business"s ability to increase efficient production, create a great deal of uncertainty.