In a commercial negotiation, a procurement professional negotiates on his company's behalf.

The assumption is false, because when a procurement professional negotiates on behalf of his employer, he brings the power of his organisation (its brand, reputation and purchasing spend) as well his own personal power (that which is embedded within him) to the negotiation.

From a negotiation perspective, both organisational and personal power have the ability to influence the behaviours of other or the cause of event. This power is clearly core to negotiation, and of enormous important in seeking to achieve the objectives.