Accident, again, is that which is not any of these, neither definition, nor property, nor genus; yet it is present with a thing, and is that which may possibly be present with some one and the same thing and may not be present, as, to sit may be and may not be present with some one and the same thing, and in like manner whiteness, for there is nothing to prevent the same thing being at one time white and at another not white. Now of these definitions of accident, the second is the better; since when the first is stated, it is necessary in order to understand it, to know previously what definition genus and property are, but the second is self-sufficient for the knowledge per se of what the thing asserted is. To accident also let comparisons of things with each other belong, in whatever way they are derived from accident, as, whether the honourable or the advantageous be preferable, and whether a life of virtue or of enjoyment is the sweeter, and if there happens to be any other assertion similar to these, for in all things of this kind, the question arises as to which the predicate rather happens to belong. Still from these it is manifest that there is nothing to prevent accident sometimes, and with reference to something, becoming property, as to sit being accident, when some one alone sits, will then be a property, but one not sitting alone, it will be a property with reference to those who do not sit, so that nothing prevents accident from becoming property in a certain relation and at a certain time; simply, however, it will not be property.
