nterpretivism (and behaviourism) opposes positivism, focusing on action theory. Human behaviour is taken to be meaningful and worthy of study beyond empiricism as it is far more than that. Interpretivists see ideas, thought and mind as mere social and mental constructs, so we cannot fully understand the world because we take our own individual view points to what is happening.
Durkheim was a positivist - he thought it both possible and desirable for sociologists to be able to establish laws of human behaviour. In his study of suicide, Durkheim found it to be the product of social forces external to the individual. People's behaviour is seen to be governed by external stimuli, and their ideas and feelings are irrelevant. As a result, the behaviour can be objectively rather than subjectively observed and measured, similar to how a scientist observes and measures the natural world.
Interpretivists or anti-positivists suggest people people apply meaning to the world, and so sociology should not even try to be scientific. Human behaviour is taken to be meaningful and so cannot be understood in the same way as natural phenomena can be. In metaphysics, a tree is a tree, there is not meaning for it being a tree, it just is. Human thoughts and ideas aren't just thoughts and ideas, they have meaning. If someone is to commit suicide then there is a meaning for them to do that. Whilst the actions of 11th September 2001 are seen by most as an act of terrorism, to those committing the acts they most likely had an entirely different meaning. Likewise, the war on terrorism can be given contradicting meanings by different individuals and societies.
To an interpretivist, reality is too complicated for numbers and quantitative analysis to be made. Qualitative methods are essential for a full understanding of social reality. Scientific objectivity cannot be upheld using these qualitative methods which require a level of subjective thought.