Hi, the nature of reality and degree of researcher's control will determine what philosophy you follow. I do both. I will give two examples:

1. I want to estimate the impact on financial development on climate change where the nature of reality is objective and i dont have any control directly on the inputs and outputs. I am in the positivit's paradigm. 

2. I go out to observe the behaviour of the entrepreneurs using ethnographic studies. I do control a lot of inputs and outputs and the nature of reality in these studies is highly subjective to various continent factors. I am in the interpretivist's paradigm.

M 

thank you for your response,

most of research methodology text books talk about one philosophy per researcher, because it is related to his/her personality and the way he.she looks so life, things, and facts. I prefer your point of view that each set of research lead themselves to one of theses perspectives.... Thank you again