An agent is systematic if, all relevant attitudes and information are communicated on all occasions when they are so relevant. For example, an agent is systematic if it/(s)he communicates (directly or indirectly) disagreement with a proposal when the agent does in fact disagree, and never communicates disagreement when this is not the case. Similarly, an agent is systematic if it/(s)he communicates information that would support or 'undermine' a proposal when the agent possesses such information, and it is relevant to communicate it. The degree of systematicity is thus a fundamental manifestation of a form of cooperative behaviour, and relates to basic maxims of cooperation such as sincerity, mendacity and helpfulness.