Philosophy affects ethical issues because a person’s ethical framework is partly built upon a person’s philosophical framework.

There is a link between philosophy and ethical behavior because philosophers describe human behavior and how humans should behave.  Ethics can be described as “a study of human behavior as a consequence of beliefs about what is right or wrong, or good or bad, insofar as that behavior is useful or effective” (philosophy.lander.edu).  In other words, we have to establish ethical principles from somewhere.  These tend to come from religion and philosophy.

The influence of religion on ethical behavior is established.  Religions determine what behavior is ethical, and followers behave thusly to avoid divine punishment.

 All religions contain specific ethical principles that believers are expected to follow. (enotes, ethics)

Therefore people must determine what ethical framework to follow.  Will they follow society’s rules, their church’s, or some others developed from philosophy.  Aristotle’s ethics, for example, focused on rational decision-making.

Aristotle replies: “Virtue makes the goal right, practical wisdom the things leading to it” (1144a7–8). By this he cannot mean that there is no room for reasoning about our ultimate end.  (http://plato.stanford.edu/)

The ends to not justify the means, in other words.  There are many philosophers who have also posited ethical theories.  A person has to make up his own mind for him or her self about what to believe.