This book examines how the law of torts, contracts, and restitution can be improved by showing how private law reduces the cost of accidents, lubricates bargains, and encourages unrequested benefits. It considers the two pervasive rules of tort law that provide incentives for actors to reduce accident costs: strict liability and negligence. It also explains how contract law achieves effiency through the remedy of damages and how restitution law allows benefactors to recover gains that their beneficiaries wrongfully obtained from them. The book makes three central claims: misalignments in tort law should be removed; in contract law, promisee's incentives should be improved; and the law should recognize some right of compensation for those who produce unrequested benefits. Each claim is based on the desire to reform private law and to make it more effective in promoting social welfare.