My turn before the rowdies get into it further...
Topic, Psychology:
Perhaps the oldest and longest running debate in the field of psychology is that of nature versus nurture, or biology versus environment (personally I prefer these two terms as they are more precise). Originally in the early days of psychology, the argument was very polarized; the great minds of the day argued for one or for the other, with the attitude that people were born into the world either as tabula rasa (blank slate), or that everything we are we are born with (or later viewed as being contained in our genetic makeup). These views were eventually discarded for the more current understanding that both are true, that it is almost never entirely nurture or nature, but ratio of both. So now the argument revolves around how much is it nurture and how much is it nature, when examining aspects of the human mind, such as personality.
In clinical practice the biology vs environment question invariably comes up when working with mental illness. The consideration of biology vs environment strongly ties into treatment planning; drugs are not a whole lot of use if the person's problems are all environmental, and therapy may not be of much benefit if the person's problems are entirely biological (there are some major exceptions to this). The problem though, is that often times it is difficult to tell what the underlying cause is; is the person depressed because they have few social contacts, or are they depressed because of a chemical imbalance that made them more anti-social and isolative, which caused the person to loose most of their social contacts. Generally speaking the answer is that both biology and environment are playing a role, and both are interacting with and influencing each other. This is why in modern clinical practice, the standard approach is to provide both drugs and therapy together to treat mental illness.
The whole process gets even more convoluted when you factor in that in clinical practice it is very common that you are not dealing with one single mental illnesses (such as depression), but multiple illnesses (such as depression + anxiety) that are interacting with and influencing each other (and each having their own biology and environment factors).
Some light reading:
http://en.wikipedia.org/wiki/Nature_...re_and_nurture