Assumptions and Conclusions - One Way Street

We start with basic assumptions of a problem space. Thats our going in position. We analyze the problem space and exit with some conclusions. These conclusions might materialize in form of policies, process definitions and other components to quantify the problem space. Here is the dilemma - how do we abstain from making the assumptions dependent on the conclusion? Its tough one to maintain, when we are sure of our target, our solution or conclusion.