Second, a maxim might fail by generating what Kant calls a "contradiction in willing." This sort of contradiction comes about when the universalized maxim contradicts something that rational agents necessarily will. For example, a person might have a maxim never to help others when they are in need. However, Kant thinks that all agents necessarily wish for the help of others from time to time. Therefore, it is impossible for the agent to will that his or her maxim be universally adopted. If an attempt to universalize a maxim results in a contradiction in conception, it violates what Kant calls a perfect duty. If it results in a contradiction in willing, it violates what Kant calls an imperfect duty. Perfect duties are negative duties, that is duties not to commit or engage in certain actions or activities (for example theft). Imperfect duties are positive duties, duties to commit or engage in certain actions or activities (for example, giving to charity).