a general sense, is that which may be predicated of a person or thing as a determining characteristic, inherent quality or accident, the negation of which involves either a falsehood, a contradiction, or an absurdity. Thus understanding is an attribute of mind, and extension an attribute of matter. That attribute which the mind conceives as the foundation of all the rest is called its essential attribute; thus extension is by some, and solidity by others, considered the essential attribute of matter.