Hickey and Lawson stress that a reflexive and rigorous scientific human geography engages with complex issues around the material and discursive forms and processes of power. Murdoch says that the sub-disciplinary division between human and physical geography has often prevented the discipline from entering fully into a relational mode of thinking. Sassen holds that particular instantiations of the local construct global formations that tend towards lateralized and horizontal networks. (pp. 155–159)