To have more freedom of debate, and that arguments may be used (pro and contra), committees of the whole House are appointed, sometimes for bills, sometimes to discuss matters of great moment. Whenever the House resolves itself into a committee, the Lord Speaker leaves the Woolsack and they or the Lord Chairman of Committees presides over the committee from the Chair; SO 29 (No Lord to speak more than once to a motion) shall not apply when the House is in committee.