A dialogue system and a method for the same are disclosed. The dialogue system includes a multimodal input unit receiving speech and non-speech information of a user, a domain reasoner, which stores a plurality of pre-stored situations, each of which is formed by a combination one or more speech and non-speech information, calculating each adaptability of the pre-stored situations on the basis of a generated situation based on the speech and the non-speech information received from the multimodal input unit, and determining a current domain according to the calculated adaptability, a dialogue manager to select a response corresponding to the current domain, and a multimodal output unit to output the response. The dialogue system performs domain reasoning using a situation including information combinations reflected in the domain reasoning process, current information, and a speech recognition result, and reduces the size of a dialogue search space while increasing domain reasoning accuracy.