Quoting from critics is done in precisely the same manner in your thesis as you have been used to using them in the past. However, what you need to keep at the forefront of your mind here is that originality is the keynote and you are using the critical quotations you have accumulated in order to establish the more firmly the niche which your research is hoping to fill. This holds true whether you are quoting in an Engineering doctorate, a Physics doctorate, an English doctorate, a History doctorate – you get the idea! It carries across the board. The critics supplement your work in all cases and need quoting as such in order to establish your work firmly within the desired framework for your PhD.
In a 1993 interview with The Washington Post, about the time the Clinton health care plan was being formulated and the thesis was being sealed, the first lady characterized her college writing as an argument against big government, supporting Alinsky's criticism of the War on Poverty programs. “I basically argued that he was right,” she told the newspaper. “Even at that early stage I was against all these people who come up with these big government programs that were more supportive of bureaucracies than actually helpful to people. You know, I've been on this kick for 25 years.”