 An emergent property of an aggregate or a whole is, very roughly, a property that is something over and above the properties of its parts and the way they are arranged in the aggregate. Broad prefers to capture this in epistemic terms: an emergent property of a whole is a property that it is impossible to logically infer from even the most complete knowledge of the properties of the parts of the whole. A property that can be so inferred is a reducible property. He captures the contrast between emergent and reducible properties in the following passage.