For example, imagine a situation where an altruistic individual lives with a group of people who are all starving. If that individual is fully altruistic, they will eventually starve to death as they would never consume food themselves but give it away to others in need. This contrived example points out the major flaw of living an entirely altruistic life, that it violates the common good by putting the individual's life and well being in harm's way. While living altruistically can be beneficial to the common good, it is limited by whether or not an individual places himself or herself in unnecessary harm. .
For a person possessing a completely egotistic nature, there is absolutely no possibility of fulfilling the common good. By acting completely egotistically, an individual exhibits a complete lack of concern for anyone other than himself or herself. While acting egotistically may be beneficial to self-preservation, it also can be detrimental to one's health. Consider an alcoholic who decides to drink and drive. By choosing to drive intoxicated, the individual shows a complete lack of concern towards anyone else as well as himself or herself by driving impaired. The potential resulting danger of driving places both the individual and others in physical danger and is in no way beneficial to the common good. Egotistical individuals are harmful to the common good as they do not provide any advantageous actions towards anyone other than themselves. .
According to Kantian ethics4, one would have to focus much more heavily on living altruistically rather than egotistically. This is because of Kant's belief that ethics are based primarily off of duty (deontology) and in order to live ethically; one must do more for others than they do for themselves. Kant's duty based ethics are primarily altruistic because of the fact that they are duty based. In order to live an ethical life according to Kant's system, an individual must perform acts, specifically altruistic acts.